$\lim_{x\to0}\left(\frac{e^{-x}-1+x^4}{sen^2x}\right)$

$\lim_{x\to0}\left(\frac{senx\left(1+cosx\right)}{xcosx}\right)$

$\left(x+4\right)\left(x-1\right)$

$16\sin b-8=0$

$\frac{1+\cos\left(x\right)}{\sin\left(x\right)}+\frac{\sin\left(x\right)}{1+\cos\left(x\right)}=2\sin\left(x\right)$

$-5x^2+15xz$

$y\left(t\right)=ce^{at}-\frac{b}{a}$