Completing the Square and Sketching a Quadratic Graph

Completing the Square and Sketching a Quadratic Graph

Secondary 3
  1. Express \({{x}^{2}}-2x-5\) in the form of \({{\left( x+a \right)}^{2}}+b\).
  2. Sketch the graph of \(y={{x}^{2}}-2x-5\) on the axes below.
    Indicate clearly the values where the graph crosses \(y\)-axes and the turning point.

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Answer:(i) \(x^2-2x-5=(x-1)^2-6\). (ii) Turning point: \((1,-6)\); \(y\)-intercept: \((0,-5)\); \(x\)-intercepts: \((1-\sqrt6,0)\) and \((1+\sqrt6,0)\).

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