$f\left(x\right)=x^4-x^3$

$f\left(x\right)=-\frac13x^3+2x^2$

$f\left(x\right)=2x^4-3x^2-0{,}5x$

$f\left(x\right)=\frac18x^3+\frac12x^2-x$

$f(x)=x^5-\frac14x^3+2x$

$f(x)=x^6-\frac23x^4+3x^2$

$f(x)=-\frac32x^4+2x^2$