$6a-2a-3a-4a-a$

$\int\frac{1}{x^2\left(x-7\right)}dx$

$-\sin\left(x\right)^2-2\cos\left(x\right)^2$

$64x-\left(-38\right)+\left(38\right)x-\left(-36\right)$

$\left(a-5+b^4\right)\left(a-5+b^4\right)$

$\sqrt[4]{81x^{18}y^{16}}$

$\sin^2\left(x\right)-\sin^4\left(x\right)+\cos^4\left(x\right)\cdot\sin^2\left(x\right)$