$\frac{x^4-4x^2+16}{x-4}$

$a^6\cdot a^4$

$\left(i^2-5\right)\left(i^4+5i^2+25\right)$

$-\frac{16}{-1}$

$-2\sin\left(x\right)\sin\left(5x\right)$

$\frac{x^2-x-12}{x^2-16}$

$\left(\frac{3}{7}a^2-\frac{2}{5}ab+\frac{3}{4}b^2\right)\cdot\:\left(\frac{5}{2}a-\frac{3}{4}b\right)$