Help with this linear algebra question

Check what the transformation does for each vector in the standard basis of R² :

T (1, 0) = (5, 2)

T (0, 1) = (-4, 0)

Now compute the weights a, b and c, d such that

a T (1, 0) + b T (0, 1) = (-2, 1)

c T (1, 0) + d T (0, 1) = (-1, 1)

Then the matrix A' is

is only a line? i think so

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a