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Question
Find fog (2) and gof (1) when : f : R → R ; f(x) = x2 + 8 and g : R → R; g(x) = 3x3 + 1.
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Solution
(fog) (2) = f (g (2)) = f (3×23+1) = f(25) = 252 + 8 = 63
(gof) (1) = g (f (1)) = g (12+8) = g (9) = 3×93+1 = 2188
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