$f\left(x\right)=15x$ ²$+4x-7$

$f\left(x\right)=3x.\ln\left(3\right)$

$f\left(x\right)=\cos x-\sin x$

$f\left(x\right)=\sec$ ²$x$

$f\left(x\right)=\frac{2}{x}$₃

$f\left(x\right)=\frac{-2}{\left(x+1\right)}$₂

$f\left(x\right)=e$ ^x$+\frac{1}{x}$

f(x)=4x/2x²+1

$f\left(x\right)=8\left(2x+1\right)$ ³

$f\left(x\right)=\frac{1}{2\sqrt{x}}+6x$ ²