WAEC Mathematics 2017 Theory — Question 13

Model answer

(i) Rewrite 2x^2-7x=26 as 2x^2-7x-9=17, i.e. y=17. Reading from the graph where y=17 gives x≈-2.20 or x≈5.78. (ii) From the graph, the minimum point of y is at approximately (2, -15). (iii) 2x^2-7x<9 means 2x^2-7x-9<0, i.e. y<0; reading the graph for the range of x where the curve is below the x-axis gives the required range of values.