Question 1048295
{{{f(x^2 +1)=x^4+5x^2+3}}}

Let {{{x = sqrt(x-1)}}}.

===> {{{f(x^2 +1) = f((sqrt(x-1))^2 +1) = f(x) = (sqrt(x-1))^4+5*(sqrt(x-1))^2+3 = (x-1)^2+5x-2 =  x^2+3x-1}}}.

===> {{{f(x^2 - 1) = (x^2 - 1)^2+3*(x^2 - 1) - 1}}},

do the rest...it will be good for you...