$5x^2+15x^4-20x^6+25x^4$

$\left(3+4y\right)^3$

$2x^2\cdot cos\left(8x\right)\cdot e^{\left(2x-2\right)}$

$3\sqrt{12}+9\sqrt{75}-12\sqrt{3}$

$\cos\left(1.6893\right)$

$\frac{\left(x+3\right)^2\cdot\:\:9-16x^2}{4x-3\cdot\:\:7x+21}$

$1-\frac{3}{x+7}=\frac{3x}{x^2+x-42}$