Question

The inverse of the matrix `[[1,-1],[2,3]]` is ...............

(A) `1/5[[3,-1],[-2,1]]`

(B) `1/5[[3,1],[-2,1]]`

(C) `1/5[[-3,1],[-2,1]]`

(D) `1/5[[3,-1],[2,-1]]`

Answer 1

(B) `1/5[[3,1],[-2,1]]`

if `A=[[a,b],[c,d]]`, then `A^-1=1/(ad-bc)[[d,-b],[-c,a]]`

`therefore A=1/5[[3,1],[-2,1]]`