Question

When graphed in the xy-plane, what is the y-coordinate of the vertex of the parabola with equation y=-3(x-4)(x+6)

Answer 1

Answer: A

Explanation:

Convert the equation into quadratic form (y=ax^2+bx+c)

y=-3(x-4)(x+6) = y=-3x^2-6x+72

Calculate -b/2a

which is 6/-6=-1

then put the value -1 into the equation for x.

-3+6+72=75

The answer is therefore A.