Graphical Solution of Quadratic Function

Graphical Solution of Quadratic Function

TGM Original

Answer the whole of this question on a sheet of graph paper.

Copy and complete the following table of values for \(y=25+4x-2{{x}^{2}}\).

\(x\)

\(-3\)

\(-2\)

\(-1\)

\(0\)

\(1\)

\(2\)

\(3\)

\(4\)

\(5\)

\(y\)

\(-5\)

\(9\)

\(a\)

\(25\)

\(27\)

\(25\)

\(19\)

\(9\)

\(-5\)

  1. Find the value of \(a\).
  2. Using a scale of \(2\) cm to represent \(1\) unit on the \(x\)-axis and \(2\) cm to represent \(5\) units on the \(y\)-axis, draw the graph of \(y=25+4x-2{{x}^{2}}\).
  3. Use your graph to estimate the solutions for the equation \(25+4x-2{{x}^{2}}=0\).
  4. By drawing a suitable straight line, estimate the solutions for the equation
    1. \(25+4x-2{{x}^{2}}=17.5\),
    2. \(25+4x-2{{x}^{2}}=-3\).

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Answer:(a) \(19\). (c) \(x\approx-2.67,4.67\). (d)(i) \(-1.18,3.18\); (ii) \(-2.87,4.87\).

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