Quadratic Graph: Maximum Point, Values, and Symmetry

Quadratic Graph: Maximum Point, Values, and Symmetry

TGM Original

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

The table below gives some \(x\) and \(y\) values of the equation \(y=-{{x}^{2}}-2x+5\).

\(x\)\(-4\)\(-3\)\(-2\)\(-1\)\(0\)\(1\)\(2\)\(3\)
\(y\)\(-3\)\(2\)\(5\)\(6\)\(5\)\(2\)\(-3\)\(a\)
  1. Find the value of \(a\).
  2. Taking \(2\)cm to represent \(1\) unit on the \(x\)-axis and \(1\) cm to represent \(1\) unit on the \(y\)-axis, draw the graph of \(y=-{{x}^{2}}-2x+5\) for \(-4\le x\le 3\).
  3. Use your graph to find
    1. the coordinates of the maximum point,
    2. the value of \(y\) when \(x=-1.5\),
    3. the values of \(x\) when \(y=4\),
    4. the equation of the line of symmetry.
  4. By drawing a suitable line, find the solutions to the equations
    1. \(-{{x}^{2}}-2x-3=0\),
    2. \(-{{x}^{2}}-x+7=0\).

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Answer:(a) \(a=-10\) (b) Graph of \(y=-x^2-2x+5\) for \(-4\leq x\leq3\) (c)(i) \((-1,6)\) (c)(ii) \(y\approx5.8\) (c)(iii) \(x\approx-2.4\) or \(0.4\) (c)(iv) \(x=-1\) (d)(i) No real solutions (d)(ii) \(x\approx-3.2\) or \(2.2\)

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