$4+\sin\left(x\right)^24\sec\left(x\right)^2=4\sec\left(x\right)^2$

$6z^2+36z+54$

$0.05x\:+200\:=\:0.07x\:+\:175$

$3^6:3^4$

$\frac{1}{3}x+6\le-1$

$\frac{x}{\left(1+x^2\right)^{\frac{1}{2}}}dx=\frac{y}{\left(1+y^2\right)^{\frac{1}{2}}}dy$

$\frac{dr}{d\theta\:}=\frac{sen\theta\:+e^{2r}sen\theta\:}{3e^r+e^rcos\theta\:}$