$$-x^2=-3x+18$$

$$10x=16x$$

$$4x^2+8x+1$$

$$50x^2-72$$

$$cos\left(4x\right)\cdot sin\left(5x\right)$$

$$\frac{1}{2}x-1=5$$

$$\frac{1}{\cot\left(x\right)^2}+\sqrt{3}\tan\left(x\right)=0$$