Solve the system of equations using a matrix.

Question

{ x + 7y = 12
{ 2x - y = 9

Answer 1

you have AX = B
where
A =
(1 7)
(2 -1)

X =
(x)
(y)

and B =
(12)
(9)
Since AX = B, X = A^-1B
A^-1 = 1/15 * A
and so
(x y) = (5 1)