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Question
If f : R → R, f(x) = x3 and g: R → R , g(x) = 2x2 + 1, and R is the set of real numbers, then find fog(x) and gof (x)
Solution
f : R → R and g : R → R
∴ f (g(x)) and g(f(x)) both are defined over common domain
f(g(x))= (g(x))3 = (2x2 + 1)3
= 8x6 + 12x4 + 6x2 + 1
g(f (x)) = 2(f(x))2 + 1 = 2(x3)2 + 1 = 2x6 + 1
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