Problem 14 - Entrance Test

Use a³ - b³ = (a-b)(a²+ab+b²). Here a = x+2, b = x-2, a-b = 4. Then 4[(x+2)² + (x+2)(x-2) + (x-2)²] = 432 → (x²+4x+4) + (x²-4) + (x²-4x+4) = 108 → 3x² + 4 = 108 → 3x² = 104 → x² = 104/3 ≈ 34.7; nearest listed choice is 32.