Find the gradient of y=x^2-6x-16 at the point where the curve crosses the x-axis

So we have y = 0 and therefore x² - 6x - 16 =0 

This is then factorised to (x+2)(x-8) = 0 and therefore we have x = -2, x = -8

To find the gradient we need to find dy/dx

So  dy/dx = 2x - 6

Therefore if x = -2,                  And if x = 8

dy/dx = 2(-2) - 6 = -10             dy/dx = 2(8) - 6 = 10