Author note — to cover

Solve quadratics already equal to zero by factorising and setting each bracket to zero, since a product vanishes only when a factor does. Foundation: monic x² + bx + c cases including the difference of two squares. Higher adds a > 1 via the harder factorising page; rearranging first is the Higher sibling. (A18)

Introduction

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Practice and continue

Practice

Solving a quadratic by factorising

Factorising, then setting each bracket to zero, since a factor must be zero.

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Quadratics with no constant term

Solving x² = 5x by factorising, since dividing by x loses the root x = 0.