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Misael Matthews

Misael Matthews

Answered question

2022-06-16

Suppose that T : R n R m is a linear transformation. Prove that there exists an m × n matrix A such that for all x R n , T ( x ) = A x. In other words, T is the "matrix transformation" associated with A.

Answer & Explanation

boomzwamhc

boomzwamhc

Beginner2022-06-17Added 17 answers

Here's a proof.
Let e 1 , , e n denote the standard basis of R n (i.e. the columns of the identity matrix). Let A be the matrix whose columns are T ( e 1 ) , , T ( e n ).
Consider any vector x = ( x 1 , , x n ) T R n . We find that
T ( x ) = T ( x 1 e 1 + + x n e n ) = x 1 T ( e 1 ) + + x n T ( e n ) = ( T ( e 1 ) T ( e n ) ) ( x 1 x n ) = A x .
So, T ( x ) = A x for every x R n .

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