Sketching a parabola from factorised form (a=1)

From a parabola in factorised form y = (x - p)(x - q) with a = 1, read off the x-intercepts, find the axis of symmetry and vertex, and sketch the upward-opening curve.

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Learning objective overview

Master Teaching Guide coverage for this objective.

Current NZC (2007)
  • NA5-9
New NZC (2026)
  • NZC26-P4-ALG-ER-P-Y10-03

Resources

Terminology

  • factorised form
  • x-intercept
  • root
  • axis of symmetry
  • vertex
  • turning point
  • y-intercept

Task goals

  • Read the two x-intercepts (roots) directly from a parabola given in factorised form y = (x - p)(x - q), including the repeated-root case y = (x - p)^2.
  • Find the axis of symmetry of a factorised-form parabola as the midpoint of its two roots, x = (p + q) / 2.
  • Find the coordinates of the vertex (turning point) by substituting the axis-of-symmetry x-value back into the equation.
  • Find the y-intercept of a factorised-form parabola by substituting x = 0.
  • Write a parabola's equation in factorised form given its roots, including a repeated root, and given the axis of symmetry plus one root.
  • Explain why the axis of symmetry sits halfway between the roots, and identify or correct a student's sign or axis-of-symmetry error made when reading factorised form.
  • Expand a factorised-form equation and compare factorised form with vertex form, describing an advantage or limitation of each.

Where this fits

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

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Sketching a parabola from factorised form (a=1)

Sketching a parabola from factorised form (a=1)

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

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