$$\frac{tan^2x}{csc^2x-1}$$

$$m-8m+2m-6$$

$$\left(x^2-yx\right)^2$$

$$\left|-\left(-5\right)+\left(-7\right)\right|$$

$$\frac{-12w^9z^4}{144w^2z^3}$$

$$9x^2-3x-5+5x-9$$

$$n\left(x-y\right)+\left(n-1\right)\left(y-x\right)$$