$\left(-xy\right)\cdot\left(-4ax^3\right)$

$\left(8e+14f\right)^2$

$\left(7-5x\right)\left(49+35x+25x^2\right)$

$\lim_{x\to0}\left(\frac{\sin\left(3x\right)-cos\left(x\right)}{sin^2\left(x\right)}\right)$

$\lim_{k\to\infty}\left(\frac{t}{\left(e^{-k}+z\right)e^{-k}}\right)$

$\frac{4}{5}x^2y-\frac{3}{7}x^2y$

$\left(-\frac{1}{2}\right)^{\infty}$