$\frac{1+\frac{sen\:x}{cos\:x}}{1+\frac{cos\:x}{sen\:x}}$

$\frac{1}{cos\:r\cdot sen\:r}$

$\left(2x+3y\right)\left(2x-3y\right)-3\left(x+2y\right)\left(x-2y\right)$

$f\left(x\right)=x^{2}-3x\quady\quadf\left(x\right)=-x^{2}+9x$

$x\left(x+1\right)\left(x-2\right)\left(x+3\right)$

$7q\:-\:15\:=\:9\:-\:5q$

$2^1+2^5$