Tentukan nilai X ( x+1 )kuadrat - ( x-1 )kuadrat = x+9

(x + 1)² - (x - 1)² = x + 9
(x + 1 + x - 1)(x + 1 - x + 1) = x + 9
(2x)(2) = x + 9
4x = x + 9
4x - x = 9
3x = 9
x = 9/3
x = 3

catatan :
a² - b² = (a + b)(a - b)