Parabolas: Vertical Scale Factor

Sketch and compare y = x^2 with y = ax^2 for simple positive integer values of a, describing the parabola as narrower or wider.

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Learning objective overview

Master Teaching Guide coverage for this objective.

Current NZC (2007)
  • NA6-7
New NZC (2026)
  • NZC26-P4-ALG-ER-P-Y10-09

Resources

Terminology

  • vertical scale factor
  • coefficient a
  • narrower / wider than y = x^2
  • stretch
  • compression
  • y = ax^2
  • y = a(x-h)^2+k

Task goals

  • Foundation: Sketch and compare y = x^2 with y = ax^2 for simple positive integer values of a, describing the parabola as narrower or wider.
  • Proficient: Determine the vertical scale factor a from a graph or table of values, including cases where 0 < a < 1 or a is negative, and write the corresponding equation.
  • Excellence: Combine a vertical scale factor with translations (y = a(x-h)^2+k) to sketch or reconstruct a full parabola equation from a labelled graph, and justify the effect of a algebraically.

Where this fits

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

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Parabolas: Vertical Scale Factor

Parabolas: Vertical Scale Factor

Do

Determining the effect on graphs in the coordinate plane of changing the coefficient of x^2 and the fixed value c, for a range of quadratic equations of the form y = ax^2 or y = x^2 + c, where a is a positive integer and c is an integer

Statement▸
Year 10 · Algebra · Equations and relationships
NZC26-P4-ALG-ER-P-Y10-09

Next

Year 10 is the last year of this phase — the curriculum lists nothing after this. Extension resources: Drawing exponential graphs, Reading and forming parabolas in vertex form y = a(x - h)^2 + k where a is not 1.

Explore the whole sequence →