WAEC 2025 · Paper 1 · Q20✱✱

The graph of $y = 3x^2 + x - 7$ is shown. Which of the following is the best estimate of the minimum value of $y$ ?

Worked solution (try it first)

The minimum value of $y$ is the $y$ -value of the lowest point of the curve.
On the graph the lowest point is just below $y = -7$ , slightly left of the $y$ -axis.
Check: the turning point is at $x = -\frac16$ , where $y = -7\frac{1}{12}$ .
The best estimate is $-7$ , option A.