$f(x)=x^2-5$

$f\left(x\right)=2x^2+4x$

$f\left(x\right)=2x^5-3x^3+x^2-10$

$f(x)=\frac{1}{2}x^4−4x^3+6x^2−4x+\frac{1}{8}$

$f(x)=\frac{1}{3}x^3−\frac{2}{5}x^2+6x$

$f(a) = 4a^4 - 3a^2 +2$

$f(x) = ax^3 - bx + c$