Question

Solve : 3x + 4y + 5z = 18, 2x – y + 8z =13 and 5x – 2y + 7z = 20 by using the matrix inversion method.

Answer 1

Let A

Given equations can be written as AX = B

By matrix inversion method X = A-1B is the solution

det A = 3(– 7 +16) – 4 (14 – 40) + 5 (– 4 + 5)

= 27 + 104 + 5

= 136

The cofactors of elements of A are

∴ x = 3, y = 1, z = 1 is the solution.