Note that f(x) = x² - 6x - 40 = 0 is the same as y = x² - 6x - 40.
To find the x of the vertex, we use the formula x = -b/2a.
So we have x = -(-6)/2(1) or x = 6/2 or x = 3.
To find the y of the vertex, we plug a 3 back in for x.
So we have y = (3)² - 6(3) - 40 or 9 - 18 - 40 which is -49.
So our vertex is the point (3,-49).
