$\left(-7x^4\:+\:2\:x\:\right)\:\left(\:5x\:+\:x^2\:\right)$

$\cos\left(x\right)\left(\sin\left(x\right)+\cos\left(x\right)\cot\left(x\right)\right)$

$5\cos\left(2x\right)=5\sin\left(x\right)^2+4$

$9x+3y+9z+7x+2y+5z+6x-7y-3z$

$\left(xy+y\right)\left(x-2y^2\right)$

$10b\:-\:30ab2\:=\:0$

$18x^2+17x-15$