Problem related to linear transformation
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Problem
Assume that a linear transformation $T$ has two eigenvectors $x$ and $y$ belonging to two distinct eigenvalue
$lambda$ and $mu$ . If $ax+by$ is an eigenvector of$T$,prove that $a=0$ or $b=0$.
Attempt
$T(x)=lambda x$ and $T(y) = mu y$.
$T(ax+by) = omega(ax+by)$,where $omega$ is an eigenvalue for $ax+by$.
$a(lambda -omega)=0$ and $b(mu-omega) =0$ since $x$ and$ y$ are independent( distinct eigenvalues)
.
Problem
How to arrive at result after that ?
linear-algebra linear-transformations
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up vote
2
down vote
favorite
Problem
Assume that a linear transformation $T$ has two eigenvectors $x$ and $y$ belonging to two distinct eigenvalue
$lambda$ and $mu$ . If $ax+by$ is an eigenvector of$T$,prove that $a=0$ or $b=0$.
Attempt
$T(x)=lambda x$ and $T(y) = mu y$.
$T(ax+by) = omega(ax+by)$,where $omega$ is an eigenvalue for $ax+by$.
$a(lambda -omega)=0$ and $b(mu-omega) =0$ since $x$ and$ y$ are independent( distinct eigenvalues)
.
Problem
How to arrive at result after that ?
linear-algebra linear-transformations
show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
Problem
Assume that a linear transformation $T$ has two eigenvectors $x$ and $y$ belonging to two distinct eigenvalue
$lambda$ and $mu$ . If $ax+by$ is an eigenvector of$T$,prove that $a=0$ or $b=0$.
Attempt
$T(x)=lambda x$ and $T(y) = mu y$.
$T(ax+by) = omega(ax+by)$,where $omega$ is an eigenvalue for $ax+by$.
$a(lambda -omega)=0$ and $b(mu-omega) =0$ since $x$ and$ y$ are independent( distinct eigenvalues)
.
Problem
How to arrive at result after that ?
linear-algebra linear-transformations
Problem
Assume that a linear transformation $T$ has two eigenvectors $x$ and $y$ belonging to two distinct eigenvalue
$lambda$ and $mu$ . If $ax+by$ is an eigenvector of$T$,prove that $a=0$ or $b=0$.
Attempt
$T(x)=lambda x$ and $T(y) = mu y$.
$T(ax+by) = omega(ax+by)$,where $omega$ is an eigenvalue for $ax+by$.
$a(lambda -omega)=0$ and $b(mu-omega) =0$ since $x$ and$ y$ are independent( distinct eigenvalues)
.
Problem
How to arrive at result after that ?
linear-algebra linear-transformations
asked Sep 1 at 6:16
blue boy
1,085513
1,085513
show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36
add a comment |Â
show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36
show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36
show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36
add a comment |Â
2 Answers
2
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3
down vote
accepted
$T(ax+by) = omega(ax+by)$, where $omega$ is an eigenvalue for $ax+by$.
As noted, by linearity $,omega(ax+by) = T(ax+by) = a T(x) + bT(y) = alambda x + b mu y,$, and by linear independence $,a lambda = a omega,$ and $,bmu = b omega,$. Multiplying the first equality by $b$ and the second one by $a$ then subtracting gives $requirecancel,balambda-abmu=baomega-abomega=0 iff ab(lambda-mu)=0,$, and since $,lambda ne mu;ldots$
add a comment |Â
up vote
2
down vote
Your approach is correct. Now that $lambda ne mu$, there can be no $omega$ that simultaneously satisfies both the equations (assuming a and b are not equal to zero). So the possible solutions are,
a or b = 0 and $omega$ taking the appropriate value to satisfy the other equation.
a, b both are 0, which means the vector becomes a 0 vector and its a trivial case.
So if ax+by is an eigenvector of T, then either a=0 or b=0.
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
$T(ax+by) = omega(ax+by)$, where $omega$ is an eigenvalue for $ax+by$.
As noted, by linearity $,omega(ax+by) = T(ax+by) = a T(x) + bT(y) = alambda x + b mu y,$, and by linear independence $,a lambda = a omega,$ and $,bmu = b omega,$. Multiplying the first equality by $b$ and the second one by $a$ then subtracting gives $requirecancel,balambda-abmu=baomega-abomega=0 iff ab(lambda-mu)=0,$, and since $,lambda ne mu;ldots$
add a comment |Â
up vote
3
down vote
accepted
$T(ax+by) = omega(ax+by)$, where $omega$ is an eigenvalue for $ax+by$.
As noted, by linearity $,omega(ax+by) = T(ax+by) = a T(x) + bT(y) = alambda x + b mu y,$, and by linear independence $,a lambda = a omega,$ and $,bmu = b omega,$. Multiplying the first equality by $b$ and the second one by $a$ then subtracting gives $requirecancel,balambda-abmu=baomega-abomega=0 iff ab(lambda-mu)=0,$, and since $,lambda ne mu;ldots$
add a comment |Â
up vote
3
down vote
accepted
up vote
3
down vote
accepted
$T(ax+by) = omega(ax+by)$, where $omega$ is an eigenvalue for $ax+by$.
As noted, by linearity $,omega(ax+by) = T(ax+by) = a T(x) + bT(y) = alambda x + b mu y,$, and by linear independence $,a lambda = a omega,$ and $,bmu = b omega,$. Multiplying the first equality by $b$ and the second one by $a$ then subtracting gives $requirecancel,balambda-abmu=baomega-abomega=0 iff ab(lambda-mu)=0,$, and since $,lambda ne mu;ldots$
$T(ax+by) = omega(ax+by)$, where $omega$ is an eigenvalue for $ax+by$.
As noted, by linearity $,omega(ax+by) = T(ax+by) = a T(x) + bT(y) = alambda x + b mu y,$, and by linear independence $,a lambda = a omega,$ and $,bmu = b omega,$. Multiplying the first equality by $b$ and the second one by $a$ then subtracting gives $requirecancel,balambda-abmu=baomega-abomega=0 iff ab(lambda-mu)=0,$, and since $,lambda ne mu;ldots$
answered Sep 1 at 6:42


dxiv
55.9k64798
55.9k64798
add a comment |Â
add a comment |Â
up vote
2
down vote
Your approach is correct. Now that $lambda ne mu$, there can be no $omega$ that simultaneously satisfies both the equations (assuming a and b are not equal to zero). So the possible solutions are,
a or b = 0 and $omega$ taking the appropriate value to satisfy the other equation.
a, b both are 0, which means the vector becomes a 0 vector and its a trivial case.
So if ax+by is an eigenvector of T, then either a=0 or b=0.
add a comment |Â
up vote
2
down vote
Your approach is correct. Now that $lambda ne mu$, there can be no $omega$ that simultaneously satisfies both the equations (assuming a and b are not equal to zero). So the possible solutions are,
a or b = 0 and $omega$ taking the appropriate value to satisfy the other equation.
a, b both are 0, which means the vector becomes a 0 vector and its a trivial case.
So if ax+by is an eigenvector of T, then either a=0 or b=0.
add a comment |Â
up vote
2
down vote
up vote
2
down vote
Your approach is correct. Now that $lambda ne mu$, there can be no $omega$ that simultaneously satisfies both the equations (assuming a and b are not equal to zero). So the possible solutions are,
a or b = 0 and $omega$ taking the appropriate value to satisfy the other equation.
a, b both are 0, which means the vector becomes a 0 vector and its a trivial case.
So if ax+by is an eigenvector of T, then either a=0 or b=0.
Your approach is correct. Now that $lambda ne mu$, there can be no $omega$ that simultaneously satisfies both the equations (assuming a and b are not equal to zero). So the possible solutions are,
a or b = 0 and $omega$ taking the appropriate value to satisfy the other equation.
a, b both are 0, which means the vector becomes a 0 vector and its a trivial case.
So if ax+by is an eigenvector of T, then either a=0 or b=0.
answered Sep 1 at 6:37
Lokesh Kumar
1363
1363
add a comment |Â
add a comment |Â
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show that if $a$ is not zero then $b=0$
– Lozenges
Sep 1 at 6:36