Question

How do you find the inverse of `A=``((18, -3), (-3, 15))`?

Answer 1

To find the inverse `A^-1`of a matrix `A` which is `2x2` the formula is

`[((a, b), (c, d))]^(-1)=1/[a*d-b*c]*[((d, -b), (-c, a))]`

Just replace for `a=18,b=-3,c=-3,d=15` to get

`A^-1=1/87*((5,1),(1,6))`