$3a+4+\sqrt{12a^{2}+34a^{2}-30}$

$86+60-12$

$3x^2yz+6xz-9yz$

$\lim_{x\to\infty}\left(\frac{x^2-2x^5}{3+7x^4}\right)$

$x^4+6x^2$

$4-10-\left\{\left[-17+20\right]-5\right\}+\left[-4+\left(4-3-5\right)\right]$

$\frac{4sin\left(x\right)}{cos^2\left(x\right)}=2\cdot sin\left(2x\right)\cdot sec^3x$