June 2017 Paper 1 Q3
3
(a) On the axes below, sketch the graph of \(\quad y = x^2 + 7x - 18\)
Label all points of intersection with the axes.
You do not need to work out the coordinates of any stationary points. [3 marks]
(b) Work out the equation of the line of symmetry of the graph of \(\quad y = x^2 + 7x - 18\) [1 mark]
| Answer | Mark | Comments |
|---|---|---|
| Fully correct curve with all intersections labelled ie. \(-9\) and 2 on the \(x\)-axis and \(-18\) on the \(y\)-axis | B3 | B2 for two correct \(x\)-axis points of intersection labelled (they must have a quadratic graph drawn in the correct orientation) B1 for U shaped curve, in the correct orientation, crossing \(y\)-axis at \(-18\), (the \(x\)-axis crossing points not labelled) or two of the three \(x\) or \(y\) axis crossing points marked or stated ... eg this could be (2, 0) and (0, \(-18\)) seen in a table of values or \((x + a)(x + b)\) with \(ab = -18\) or \(a + b = +7\) |
Additional guidance
Table of values, points plotted and graph drawn, fully correct, scores all 3 marks
Minimum point must be to the left of the \(y\)-axis to score full marks.
Both sides of the graph must be drawn above the \(x\)-axis to score full marks
Maximum of B1 if no graph drawn eg \(x = -9\) and \(x = 2\) stated, but no graph
| Answer | Mark | Comments |
|---|---|---|
| \(x = -3.5\) | B1 | oe |
Additional guidance
It must be \(x = -3.5\), do not accept \(y = -3.5\) or \(-3.5\) on its own