Find max point of y=-x^2-5x-10

Can either differentiate or using the completing the square method. Differentiation not covered at GCSE so completing the square should be done to get -((x+5/2)²+15/4). To find the max point we need to find the minimum value of (x+5/2)². This is 0 (due to square) which occurs when x=-5/2 in which case y=-15/4. This can easily be done by equating the x value to the negative of the value within the inner bracket and y value to the value in the outer bracket.