$15=u+7$

$\cos\left(x\right)=\frac{1}{6}$

$\int-\frac{1}{x^2\cdot\sqrt{4\cdot x+1}}dx$

$\frac{d}{dx}-8x^2\:+\:5xy\:+\:y^3\:=\:-149$

$\frac{2x^3+1}{3x^2+6}$

$\:7\left(7g\right)$

$\csc\left(x\right)\cdot\left(\sin\left(x\right)+\sin\left(x\right)\cdot\tan\left(x\right)^2\right)=\sec\left(x\right)^2$