1.

If f(x) = x3 + x - 5 and g(x) be another function such that g(f(x))  =x then find the value of g'(63)(1) \(\frac1{50}\)(2) \(\frac1{49}\)(3) \(\frac1{48}\)(4) \(\frac1{47}\)

Answer»

Correct option is (2) \(\frac1{49}\) 

\(g' (f(x)) = \frac1 {f'(x)}\)   .....(1)

to find g'(63) put f(x) = 63

x3 + x - 5 = 63

x(x2 + 1) = 68

⇒ x = 4

Now f'(x) = 3x2 + 1

⇒ f'(4) = 49

then the value of g'(63) = \(\frac1{49}\) 



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