Solve :

(x² + 5x + 4)(x² + 5x + 6) = 120

Solve: 5^x+1 + 5^2-x = 5³ + 1

If 3x² - kx - 15 = (3x - 5)(x + 3), the value of k is :

1. 4

2. -4

3. 3

4. -3