a³ - b³ = (a - b)(a² + ab + b²)
(1-4x) (1+4x+16x^2)+x^2(64x-25)=0
1³-(4x)³ +64x^3-25x^2=0
1 - 64x^3 + 64x^3 - 25x^2 = 0
25x^2 = 1
x^2 = 1/25
|x| = 1/5
x = ± 1/5
