Function transformation: shrink horizontally

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Write the formula for $f(x)$, if the graph of $f$ can be obtained from the graph of $y = g(x)$ by shrink horizontally by a factor of $5$ then shift left $3$ units
The equation should be
$f(x) = g(5(x+3))$ or $gleft(frac15(x+3)right)$?
I prefer the second answer but my teacher said the correct is the first one? Can anyone explain for me why it is $5$ instead of $frac15$ while we are dealing with horizontal shrinking?
Thanks a lot










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    Write the formula for $f(x)$, if the graph of $f$ can be obtained from the graph of $y = g(x)$ by shrink horizontally by a factor of $5$ then shift left $3$ units
    The equation should be
    $f(x) = g(5(x+3))$ or $gleft(frac15(x+3)right)$?
    I prefer the second answer but my teacher said the correct is the first one? Can anyone explain for me why it is $5$ instead of $frac15$ while we are dealing with horizontal shrinking?
    Thanks a lot










    share|cite|improve this question









    New contributor




    TrÆ° Bát Giới is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      Write the formula for $f(x)$, if the graph of $f$ can be obtained from the graph of $y = g(x)$ by shrink horizontally by a factor of $5$ then shift left $3$ units
      The equation should be
      $f(x) = g(5(x+3))$ or $gleft(frac15(x+3)right)$?
      I prefer the second answer but my teacher said the correct is the first one? Can anyone explain for me why it is $5$ instead of $frac15$ while we are dealing with horizontal shrinking?
      Thanks a lot










      share|cite|improve this question









      New contributor




      TrÆ° Bát Giới is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      Write the formula for $f(x)$, if the graph of $f$ can be obtained from the graph of $y = g(x)$ by shrink horizontally by a factor of $5$ then shift left $3$ units
      The equation should be
      $f(x) = g(5(x+3))$ or $gleft(frac15(x+3)right)$?
      I prefer the second answer but my teacher said the correct is the first one? Can anyone explain for me why it is $5$ instead of $frac15$ while we are dealing with horizontal shrinking?
      Thanks a lot







      algebra-precalculus functions






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      edited 34 mins ago









      Larry

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      asked 44 mins ago









      TrÆ° Bát Giới

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          3 Answers
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          I found this counterintuitive when I was first learning algebra too.



          Think about it like this: $f(5x)$ gives you $f(0)$ at $x=0$, then $f(5)$ at $x=1$, then $f(10)$ at $x=2$. Varying the input parameter from $0$ to $2$ made the function go all the way from $f(0)$ to $f(10)$. So the section of the graph of $f(x)$ that used to have width 10 will have only width 2 in the graph of $f(5x)$.



          If that still doesn't click, I would just suggest drawing out a bunch of explicit examples for different functions $f$.






          share|cite|improve this answer



























            up vote
            1
            down vote













            Intuitively, a function that's shrunk covers its original range values on a shorter interval. With $5x$ instead of $x$, consider the original function on the interval $[0,1]$, you get $5cdot(1/5) =1$, so that the function covered all its original values on $[0,1]$ by the time you get to $x=1/5$, i.e on the interval $[0,1/5]$. In general then it covers its range 5 times faster.



            Another easy way is to consider $cx$ for $c$ getting really large. Then for small $x$, you've already covered a huge portion of the function's range.






            share|cite|improve this answer



























              up vote
              1
              down vote













              To shrink a function means to make the graph of the function seems narrower.



              For example, consider the function
              $$f(x)=x^2$$
              If you want to make the function shrink horizontally by a factor of 2 you would want the function
              $$f(2x) = (2x)^2 = 4x^2$$
              On the other hand, you would argue that
              $$fleft(frac12xright) = left(frac12xright)^2 = frac14x^2$$
              is correct.



              If you graph the functions, you would get



              enter image description hereenter image description hereenter image description here



              Obviously, the function $f(2x) = (2x)^2 = 4x^2$ seems narrower. Similarly, your question is asking you to shrink the function by a factor of five, so it should be $f(5x)$ instead of $fleft(frac15xright)$.






              share|cite|improve this answer




















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                3 Answers
                3






                active

                oldest

                votes








                3 Answers
                3






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes








                up vote
                3
                down vote













                I found this counterintuitive when I was first learning algebra too.



                Think about it like this: $f(5x)$ gives you $f(0)$ at $x=0$, then $f(5)$ at $x=1$, then $f(10)$ at $x=2$. Varying the input parameter from $0$ to $2$ made the function go all the way from $f(0)$ to $f(10)$. So the section of the graph of $f(x)$ that used to have width 10 will have only width 2 in the graph of $f(5x)$.



                If that still doesn't click, I would just suggest drawing out a bunch of explicit examples for different functions $f$.






                share|cite|improve this answer
























                  up vote
                  3
                  down vote













                  I found this counterintuitive when I was first learning algebra too.



                  Think about it like this: $f(5x)$ gives you $f(0)$ at $x=0$, then $f(5)$ at $x=1$, then $f(10)$ at $x=2$. Varying the input parameter from $0$ to $2$ made the function go all the way from $f(0)$ to $f(10)$. So the section of the graph of $f(x)$ that used to have width 10 will have only width 2 in the graph of $f(5x)$.



                  If that still doesn't click, I would just suggest drawing out a bunch of explicit examples for different functions $f$.






                  share|cite|improve this answer






















                    up vote
                    3
                    down vote










                    up vote
                    3
                    down vote









                    I found this counterintuitive when I was first learning algebra too.



                    Think about it like this: $f(5x)$ gives you $f(0)$ at $x=0$, then $f(5)$ at $x=1$, then $f(10)$ at $x=2$. Varying the input parameter from $0$ to $2$ made the function go all the way from $f(0)$ to $f(10)$. So the section of the graph of $f(x)$ that used to have width 10 will have only width 2 in the graph of $f(5x)$.



                    If that still doesn't click, I would just suggest drawing out a bunch of explicit examples for different functions $f$.






                    share|cite|improve this answer












                    I found this counterintuitive when I was first learning algebra too.



                    Think about it like this: $f(5x)$ gives you $f(0)$ at $x=0$, then $f(5)$ at $x=1$, then $f(10)$ at $x=2$. Varying the input parameter from $0$ to $2$ made the function go all the way from $f(0)$ to $f(10)$. So the section of the graph of $f(x)$ that used to have width 10 will have only width 2 in the graph of $f(5x)$.



                    If that still doesn't click, I would just suggest drawing out a bunch of explicit examples for different functions $f$.







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered 31 mins ago









                    Nathaniel Mayer

                    1,270411




                    1,270411




















                        up vote
                        1
                        down vote













                        Intuitively, a function that's shrunk covers its original range values on a shorter interval. With $5x$ instead of $x$, consider the original function on the interval $[0,1]$, you get $5cdot(1/5) =1$, so that the function covered all its original values on $[0,1]$ by the time you get to $x=1/5$, i.e on the interval $[0,1/5]$. In general then it covers its range 5 times faster.



                        Another easy way is to consider $cx$ for $c$ getting really large. Then for small $x$, you've already covered a huge portion of the function's range.






                        share|cite|improve this answer
























                          up vote
                          1
                          down vote













                          Intuitively, a function that's shrunk covers its original range values on a shorter interval. With $5x$ instead of $x$, consider the original function on the interval $[0,1]$, you get $5cdot(1/5) =1$, so that the function covered all its original values on $[0,1]$ by the time you get to $x=1/5$, i.e on the interval $[0,1/5]$. In general then it covers its range 5 times faster.



                          Another easy way is to consider $cx$ for $c$ getting really large. Then for small $x$, you've already covered a huge portion of the function's range.






                          share|cite|improve this answer






















                            up vote
                            1
                            down vote










                            up vote
                            1
                            down vote









                            Intuitively, a function that's shrunk covers its original range values on a shorter interval. With $5x$ instead of $x$, consider the original function on the interval $[0,1]$, you get $5cdot(1/5) =1$, so that the function covered all its original values on $[0,1]$ by the time you get to $x=1/5$, i.e on the interval $[0,1/5]$. In general then it covers its range 5 times faster.



                            Another easy way is to consider $cx$ for $c$ getting really large. Then for small $x$, you've already covered a huge portion of the function's range.






                            share|cite|improve this answer












                            Intuitively, a function that's shrunk covers its original range values on a shorter interval. With $5x$ instead of $x$, consider the original function on the interval $[0,1]$, you get $5cdot(1/5) =1$, so that the function covered all its original values on $[0,1]$ by the time you get to $x=1/5$, i.e on the interval $[0,1/5]$. In general then it covers its range 5 times faster.



                            Another easy way is to consider $cx$ for $c$ getting really large. Then for small $x$, you've already covered a huge portion of the function's range.







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered 29 mins ago









                            Alex R.

                            23.9k12352




                            23.9k12352




















                                up vote
                                1
                                down vote













                                To shrink a function means to make the graph of the function seems narrower.



                                For example, consider the function
                                $$f(x)=x^2$$
                                If you want to make the function shrink horizontally by a factor of 2 you would want the function
                                $$f(2x) = (2x)^2 = 4x^2$$
                                On the other hand, you would argue that
                                $$fleft(frac12xright) = left(frac12xright)^2 = frac14x^2$$
                                is correct.



                                If you graph the functions, you would get



                                enter image description hereenter image description hereenter image description here



                                Obviously, the function $f(2x) = (2x)^2 = 4x^2$ seems narrower. Similarly, your question is asking you to shrink the function by a factor of five, so it should be $f(5x)$ instead of $fleft(frac15xright)$.






                                share|cite|improve this answer
























                                  up vote
                                  1
                                  down vote













                                  To shrink a function means to make the graph of the function seems narrower.



                                  For example, consider the function
                                  $$f(x)=x^2$$
                                  If you want to make the function shrink horizontally by a factor of 2 you would want the function
                                  $$f(2x) = (2x)^2 = 4x^2$$
                                  On the other hand, you would argue that
                                  $$fleft(frac12xright) = left(frac12xright)^2 = frac14x^2$$
                                  is correct.



                                  If you graph the functions, you would get



                                  enter image description hereenter image description hereenter image description here



                                  Obviously, the function $f(2x) = (2x)^2 = 4x^2$ seems narrower. Similarly, your question is asking you to shrink the function by a factor of five, so it should be $f(5x)$ instead of $fleft(frac15xright)$.






                                  share|cite|improve this answer






















                                    up vote
                                    1
                                    down vote










                                    up vote
                                    1
                                    down vote









                                    To shrink a function means to make the graph of the function seems narrower.



                                    For example, consider the function
                                    $$f(x)=x^2$$
                                    If you want to make the function shrink horizontally by a factor of 2 you would want the function
                                    $$f(2x) = (2x)^2 = 4x^2$$
                                    On the other hand, you would argue that
                                    $$fleft(frac12xright) = left(frac12xright)^2 = frac14x^2$$
                                    is correct.



                                    If you graph the functions, you would get



                                    enter image description hereenter image description hereenter image description here



                                    Obviously, the function $f(2x) = (2x)^2 = 4x^2$ seems narrower. Similarly, your question is asking you to shrink the function by a factor of five, so it should be $f(5x)$ instead of $fleft(frac15xright)$.






                                    share|cite|improve this answer












                                    To shrink a function means to make the graph of the function seems narrower.



                                    For example, consider the function
                                    $$f(x)=x^2$$
                                    If you want to make the function shrink horizontally by a factor of 2 you would want the function
                                    $$f(2x) = (2x)^2 = 4x^2$$
                                    On the other hand, you would argue that
                                    $$fleft(frac12xright) = left(frac12xright)^2 = frac14x^2$$
                                    is correct.



                                    If you graph the functions, you would get



                                    enter image description hereenter image description hereenter image description here



                                    Obviously, the function $f(2x) = (2x)^2 = 4x^2$ seems narrower. Similarly, your question is asking you to shrink the function by a factor of five, so it should be $f(5x)$ instead of $fleft(frac15xright)$.







                                    share|cite|improve this answer












                                    share|cite|improve this answer



                                    share|cite|improve this answer










                                    answered 12 mins ago









                                    Larry

                                    382117




                                    382117




















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