Question

What substitution should be used to rewrite 4x12 – 5x6 – 14 = 0 as a quadratic equation?
u = x2
u = x3
u = x6
u = x12

Answer 1

Use u = x^6. Then x^12 = u^2 and x^6 = u, so the equation becomes 4u^2 − 5u − 14 = 0, a quadratic.