Q5 of 64 Page 10

If f (x) = x3 + 7x2 + 8x – 9, find f ‘ (4).

We are given with a polynomial function f(x) = x3 + 7x2 + 8x - 9, and we have to find whether it is derivable at x = 4 or not, so by using the formula, f ‘(c) = , we get,

f ‘(4) =


f ‘(4) =


f ‘(4) =


f ‘(4) = limx→4 x2 + 11x + 52


f ‘(4) = 112.


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