$2x^2-3x-1-x^2+3x+2$

$2\cdot20+-40$

$\lim_{x\to0}\left(\frac{2x}{1\:-\:cos\left(x\right)}\right)$

$x\left(t\right)cos\left(z\left(t\right)+y\left(t\right)\right)=x\left(t\right)cos\left(z\left(t\right)\right)+y\left(t\right)sin\left(z\left(t\right)\right)$

$\frac{16g^4-81}{2g+3}$

$9b^2-30a^2b+25^4$

$-\left(-3.8b-7c-5.4\right)$