(Original post by purple-owl)
It's so much easier when you have the actual graph for it but the thing is I don't know how to draw the graph for that function! (and I won't have WolframAlpha in the exam either)
You should know how to draw quadratics. A quadratic with a positive x^2 term generates a U shape or "happy face" parabola and a negative x^2 quadratic (like the one in your question) is a "sad face" parabola.
Every "sad face" quadratic has a maximum so think about what I said in my last post to determine where it is.