Question 1094739
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Simply substitute the expression for g(x) = 2x+1 into f(x), replacing x in f(x) by this expression:


f(g(x)) = f(2x+1) = {{{(2x+1)^2}}}. 


That's all.


If you wish, you may transform this resulting expression  {{{(2x+1)^2}}}  in any way you want.