$\frac{x^2}{x^2+10+25}$

$cos^2\:x\:-\frac{1}{2}=0$

$\left(x+3\right)\left(x-3\right)-\left(x+3\right)^2+18$

$y+2y'+y=2e^{\left(-x\right)}$

$2\left(t-4\right)+1$

$-28x^3+135x^2-45x$

$\left(\frac{\left(18\right)^6x\left(54\right)^{-3}x\left(8\right)^{-6}x\left(36\right)^2}{\left(24\right)^{-2}x\left(3\right)^{-6}\:x\left(0.5\right)^4x\left(27\right)^5}\right)$