Quadratic Functions, Equations and Inequalities - Nature of Roots of Quadratic Equations

Quadratic Functions, Equations and Inequalities - Nature of Roots of Quadratic Equations

Secondary 4
9 marks

A quadratic curve is given by \(y=hx^2-2x-9h+6\), where \(h\) is a constant.

  1. Show that the equation \(y=0\) has real roots for all values of \(h\) except \(h=0\).[3]
  2. State the value of \(h\) in the case where \(y=0\) has two real and equal roots.[1]
  3. Given that the line \(y=2x-h-12\) meets the curve \(y=hx^2-2x-9h+6\), find the range of values of \(h\).[5]

Solution:

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Answer:(a) \(D=4(3h-1)^2\ge0\), so \(y=0\) has real roots for all \(h\ne0\). (b) \(h=\frac{1}{3}\). (c) \(h\le\frac{1}{4},\ h\ne0\) or \(h\ge2\).

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