Question 146847
I think these are your two equations.
{{{f(x)=sqrt(x+3*sqrt(x+3))}}}
{{{g(x)=x^2}}}
For the first substitute {{{x^2}}} wherever there is an x in f.
f(g(x))={{{sqrt(x^2+3*sqrt(x^2+3))}}}
Next, substitute f(x) whereever there is an x in g.
g(f(x))={{{(sqrt(x+3*sqrt(x+3)))^2}}}
g(f(x))={{{x+3*sqrt(x+3)}}}