$13b+10b-7b\left(b=2\right)$

$\frac{sen\left(\frac{\left(x+1\right)}{\sqrt{y}}\right)}{cos\left(\frac{\left(x+1\right)}{\sqrt{y}}\right)}$

$\lim_{x\to1}\frac{x+2}{\left(x^2-2x+1\right)}$

$\left(4x^2+9y\right)\left(4x^2-9y\right)$

$\lim_{h\to0}\left(\frac{\sqrt{36+h}+6}{h}\right)$

$\left(1950\right)+\left(20\right)$

$6xy+8x+15y+20$