$-3\sin\left(t\right)=15\cos\left(t\right)\sin\left(t\right)$

$\lim_{x\to0}\left(\frac{ln\left(6+5x\right)}{x+1}\right)$

$x^3y^2-x^3y$

$\left(3y^4-8z\right)\left(3y^4+8z\right)$

$25x^2-45x+81$

$-15+\left(-6\right)-\left(-4\right)\cdot\left(-6\right)$

$\left(x^2-49x\right)\:\left(x+7\right)$