( x + 1/2 )³ -x³ = 7/8

( x + 1/2 )³ - x³ = 7/8
x³ + 3/2x² + 3/4x + 1/8 - x³ = 7/8
3/2x² + 3/4x + 1/8 = 7/8
3/2x² + 3/4x = 6/8  (kedua ruas dikali 8)
12x² + 6x = 6
12x² + 6x - 6 = 0
12x² + 12x - 6x - 6 = 0
12x(x + 1) - 6(x + 1) = 0
(12x - 6)(x + 1) = 0

12x = 6
    x  = 2

atau
x = -1