Tangent lines with zero slope

a). Graph the function f(x) = 4 – x^2

b). Identify the point (a, f(a)) at which the fuction has a tangent line with zero slope.

c). consider the point (a, f(a)) found in part (b). is it true that the secant line between (a-h, f(a-h)) and (a+h, f(a+h)) has slope zero for any value of h # 0?.

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