Question

Solve for x: `|(1,−2,5 ),(2,x,−1),(0,4,2x)|` = 86

Answer 1

1(2x² + 4) + 2 (4x − 0) + 5(8 − 0) = 86

2x² + 4 + 8x + 40 − 86 = 0   ...[Simplify]

2x² + 8x + 44 − 86 = 0

2x² + 8x − 42 = 0

x² + 4x − 21 = 0    ...[Divide by 2]

(x + 7) (x − 3) = 0   ...[Factorize]

x = −7 or x = 3