If f’(x) = 8x3 – 2x, f(2) = 8, find f(x).

Given f’(x) = 8x3 – 2x and f(2) = 8


On integrating the given equation, we have



We know





Recall




f(x) = 2x4 – x2 + c


On substituting x = 2 in f(x), we get


f(2) = 2(24) – 22 + c


8 = 32 – 4 + c


8 = 28 + c


c = –20


On substituting the value of c in f(x), we get


f(x) = 2x4 – x2 + (–20)


f(x) = 2x4 – x2 – 20


Thus, f(x) = 2x4 – x2 – 20


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