$4=-25-k$

$\left(1-\tan\theta\right)^{2}=\sec^{2}\theta-2\tan\theta$

$\left(2a^2-3b+4c^3\right)^2$

$\left(4a^2-3b^3\right)\left(4a^2-3b^3\right)$

$cos\:\left(3x\right)cos\left(x\right)-\sin\left(3x\right)\cdot\sin\left(x\right)=1$

$\frac{dy}{dx}=2t$

$\int\left(9x^3-13\right)^627x^2dx$