WAEC 2020 · Paper 1 · Q48

The graphs of $y = 2x + 5$ and $y = 2x^2 + x - 1$ are shown. Find the points of intersection of the two graphs.

The vertical scale is a quarter of the horizontal scale.

Where do the line and the curve meet?

Worked solution (try it first)

Where the graphs meet, $2x^2 + x - 1 = 2x + 5$ .
Bring everything to one side: $2x^2 - x - 6 = 0$ .
Factorise: $(2x + 3)(x - 2) = 0$ , so $x = 2$ or $x = -1.5$ .
Find $y$ from the line $y = 2x + 5$ : $x = 2$ gives $y = 9$ , and $x = -1.5$ gives $y = 2$ .
So the points are $(2.0, 9.0)$ and $(-1.5, 2.0)$ , option A.