Question

If $f:R\to R$ is defined by $f(x)=x^2-3x+2,find \,f(f(x)).$

Answer 1

It is given that $f:R\to R \,is\,defined \,as f(x)=x^2-3x+2$.
$f(f(x))=f(x^2-3x+2)$
= $(x^2-3x+2)^2-3(x^2-3x+2)+2$
= $x^4+9x^2+4-6x^3-12x+4x^2-3x^2+9x-6+2$
= $x^4-6x^3+10x^2-3x$.