Question

Solve the cubic equation: 2x³ – x² – 18x + 9 = 0 if sum of two of its roots vanishes.

Answer 1

The given equation is 2x³ – x² – 18x + 9 = 0

Let the roots be α, -α, β

α² = 9

α = ±3 

The roots are 3, -3, 1/2