Question

Solve the following quadratic equation by factorisation method:

x² + x – 20 = 0

Answer 1

x² + x – 20 = 0

∴ x² + 5x − 4x − 20 = 0

∴ x(x + 5) – 4(x + 5) = 0

∴ (x + 5)(x – 4) = 0

∴ (x + 5) = 0 or (x – 4) = 0

∴ x + 5 = 0 or x – 4 = 0

∴ x = – 5 or x = 4

∴ – 5 and 4 are roots of the given quadratic equation.