$\cot^2\left(x\right)+\csc^2\left(x\right)=2\csc^2\left(x\right)-1$

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

$x^2-26x+49$

$\left(3a^2-5b\right)^2;\:a=1;\:b=-1$

$\frac{cos^2x-1}{tan\left(x\right)}$

$\left(tanx+1\right)\left(\sqrt{3}tan\:x-1\right)$

$100\:.\:-2400$