7x2 + 4x – 20 = 0

(xv) 7x² + 4x – 20 = 0

Sol. 7x² + 4x – 20 = 0

∴  7x² + 14x – 10x – 20 = 0

∴  7x (x + 2) – 10 (x + 2) = 0

∴ (x + 2) (7x – 10) = 0

∴ x + 2 = 0 or 7x – 10 = 0

∴ x = – 2 or 7x = 10

∴ x = – 2 or x = ¹⁰/₇