A student factorises as

MATHEMATICS · Single correct · AoPS · Mathematics · Quadratic Equations - Part 1 · Quadratic Equations - Part 1

Problem

A student factorises x2+4x−12x^{2}+4x-12 as (x−2)(x+6)(x-2)(x+6). Which of the following statements is correct? (a) The factorisation is correct, but the roots should be x=−2, 6x=-2,\,6. (b) The factorisation and the roots x=2, −6x=2,\,-6 are both correct. (c) The factorisation is incorrect because both brackets should have '+': (x+2)(x+6)(x+2)(x+6). (d) The factorisation is incorrect because the product of the constant terms is +12+12, not −12-12.

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