Question

If A = [(3,2,1)(4,-1,2)(7,3,-3)],then find A-1 and hence solve the following system of equations : 3x+4y+7z = 14. 2x-y+3z = 4. x+2y-3z = 0

Answer 1

|A| = 3(3-6) + (-2)(-12-14) + 1(12 + 7) = 62 ≠ 0

Hence,A-1 exists. Let cij represent the cofactor of (i,j)th element of A. Then,