$$l3l$$

$$f^2+40-f^2$$

$$f\left(x\right)=\left(senx-cosx\right)\left(senx+cosx\right)+2cos2x$$

$$\int\frac{x}{\sqrt{8-x^2-x^4}}dx$$

$$\lim_{x\to-3}\left(\frac{\sqrt{7+y}-2}{y+3}\right)$$

$$\left(xy+y^2+x^2\right)dx=x^2dy$$

$$z3\:+\:729$$