$\cos\left(x\right)\left(1+\sec\left(x\right)\right)+sec\left(1-\cos\left(x\right)\right)-\sec\left(x\right)$

$\lim_{x\to2}\sqrt{6x+13}$

$sin^2x-1+sin^2x$

$\left(23x^2+5y\right)+\left(16x^2-3y\right)+\left(14x^2-y\right)+\left(31x^2+y\right)$

$7y^2-2y-5$

$36x^2+84x-49$

$3x^2+12x=2$