Step-by-step explanation:
x^2 + 4x - 21 = 0
(x - 3)(x + 7) = 0
x = 3 or x = -7
x^2 - 14x = -24
x^2 - 14x + 24 = 0
(x - 12)(x - 2) = 0
x - 12 = 0 or x - 2 = 0
x = 12 or x = 2
2x^2 - 12 = 2x
x^2 - x - 6 = 0
(x - 3)(x + 2) = 0
x = 3 or x = -2
Topic: Factorisation
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