Which equation reveals the minimum or maximum value of f (x) without changing the form of the equation?
)A) ƒ (x) = (x+3)(x − 4)
(B) ƒ (x) = x² - 8x +15
(C)ƒ (x) = (x + 2)² − 1
(D) f(x) =x^2 +2x -1