1.

If f : R → R, f(x) = 2x + 1 and g : R → R, g(x) = x3, then (gof)-1(27) is equal to :(a) 2(b) 1(c) -1(d) 0

Answer»

Answer is (b)

Let (gof)-1(27) = x

∴ (gof)(x) = 27

g{f(x)} = 27

g{2x + 1} = 27

(2x + 1)3 = 27

2x + 1 = 271/3

2x + 1 = 33 x 1/3

2x + 1 = 3

∴ 2x = 2

x = 1



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