You have the following functions:
f(x) = 2x + 1
g(x) = x² + 7
In order to find an expression for f(g(x)) you simply replace the function g(x) where x is in f(x), just as follow:
f(g(x)) = 2g(x) + 1 replace g(x) = x² + 7
f(g(x)) = 2(x² + 7) + 1 apply distribution property
f(g(x)) = 2(x²) + 2(7) + 1
f(g(x)) = 2x² + 14 + 1 simplify like terms
f(g(x)) = 2x² + 15
Hence, the expression for f(g(x)) is 2x² + 15
