$+7-\left(+3+5\right)$

$3,3-5,5$

$y''+4y'+3y=0$

$\sec\left(a\right)\cdot\tan\left(a\right)\cdot\csc\left(a\right)=\frac{1}{\cos^2\left(a\right)}$

$4x^2+8x$

$f\left(x\right)=x^3\left(4x^2-5x-6\right)$

$\frac{1}{1-\cos\left(x\right)}+\frac{1}{1+cos\left(x\right)}=2csc^2x$