What is the y -value of the vertex of the function f of x is equal to negative open paren x plus 8 close paren times open paren x minus 14 close paren ?

The zeros are x = −8 and x = 14, so the vertex lies halfway between them at x = (−8 + 14) / 2 = 3. Substituting x = 3 gives f(3) = −(3 + 8)(3 − 14) = −(11)(−11) = 121, so the y-value of the vertex is 121.

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