Who’s the the y-value of the vertex of the function f(x)=-(x+8)(x-14)

The required y-value is -121.

Step-by-step explanation:

There are several ways in which we could approach this problem.  From the two binomial factors (x + 8) and (x - 14), we know that the two roots are x = -8 and x = 14.  The axis of symmetry is the vertical line x = 3.  This value is halfway between x = -8 and x = 14.

Substituting x = 3 into  f(x)= -(x+8)(x-14) results in f(3) = -(11)(-11) = -121.

The vertex is at (3, -121).  The required y-value is -121.