Question 18Let $f$ be a polynomial function such that, for all real $x,$ $$ f(x^2+1)=x^4+5x^2+3. $$ For all real $x,$ $f(x^2-1)$ is$x^4+5x^2+1$$x^4+x^2-3$$x^4-5x^2+1$$x^4+x^2+3$none of these