Solving Factorised Equations (Null Factor Law)

Solve two-factor equations of the form $(x-a)(x-b)=0$ by applying the null factor law directly.

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Learning objective overview

Master Teaching Guide coverage for this objective.

Current NZC (2007)
  • NA5-7
New NZC (2026)
  • NZC26-P4-ALG-ER-P-Y10-03
  • NZC26-P4-ALG-ER-K-Y10-05

Resources

Terminology

  • null factor law
  • factorised form
  • factor
  • product
  • solve
  • coefficient
  • extraneous solution

Task goals

  • Foundation: Solve two-factor equations of the form $(x-a)(x-b)=0$ by applying the null factor law directly.
  • Proficient: Solve equations with three factors, a repeated factor, or a leading coefficient inside one bracket, e.g. $(2x-1)(x+4)=0$ or $x(x-5)(x+2)=0$.
  • Excellence: Rearrange non-zero-product equations into factorised = 0 form first (e.g. moving all terms to one side) before applying the null factor law, including checking for extraneous or repeated solutions.

Where this fits

What leads into this objective, and where it goes next.

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Solving Factorised Equations (Null Factor Law)

Solving Factorised Equations (Null Factor Law)

Do

Solving quadratic equations that are factorised or of the form x^2 + c = 0 (where c is an integer), and connecting the solutions to the x-intercepts of the related graph

Statement▸
Year 10 · Algebra · Equations and relationships
NZC26-P4-ALG-ER-P-Y10-03
Know

The zero product property states that if two expressions multiply to be zero, then at least one expression must be zero (e.g. if ab = 0 then either a or b is 0, or if (x − a)(x − b) = 0 then either (x − a) = 0 or (x − b) = 0).

Statement▸
Year 10 · Algebra · Equations and relationships
NZC26-P4-ALG-ER-K-Y10-05

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