JAMB Mathematics 2013 Paper

Concept:A quadratic graph crosses the x-axis at values of $x$ that make $y = 0$. These roots correspond to the factors of the quadratic expression.Explanation:From the graph, the curve intersects the x-axis at $x = -1$ and $x = 2$.Hence, $x = -1$ gives the factor $(x + 1)$, and $x = 2$ gives the factor $(x - 2)$.So the quadratic equation must be $y = (x + 1)(x - 2)$.Expand the brackets: $(x + 1)(x - 2) = x^2 - 2x + x - 2$.Combine like terms: $x^2 - 2x + x = x^2 - x$.Therefore, the equation simplifies to $y = x^2 - x - 2$.This matches the correct option given.Answer:$y = x^2 - x - 2$