Factorise it, it will be (x+2)(x-1) take the average of -2 and 1 (the opposites of the factored numbers) so the average is -2+1/2 which equals -1/2 now sub -1/2 into the factored expression, giving -1/2 (-1/2+4/2)(-1/2-2/2) simplying this we get 3/2 times -3/2 which equals -9/4 so the coordinates of the turning point are -1/2 and -9/4, now look at the graph, look where the graph touches the x axis, it is at -2 and 1, so these are your (roots).
