WAEC Mathematics 2015 Paper

Concept:When two graphs are drawn on the same axes, the points where they meet satisfy both equations at the same time.Explanation:Ada has drawn $y = x^2 - x - 2$ and $y = 2x - 1$.At any intersection point, the $y$-value from both graphs is the same.So she equates the two expressions for $y$:$$x^2 - x - 2 = 2x - 1$$Collect all terms on one side to form a quadratic equation:$$x^2 - x - 2 - 2x + 1 = 0$$Simplify the like terms:$$x^2 - 3x - 1 = 0$$This is the equation that gives the $x$-coordinates of the points where the line and the curve intersect.Therefore, Ada is solving the equation $x^2 - 3x - 1 = 0$.Answer:Option B. $x^2 - 3x - 1 = 0$