$$6x^2+4\left(x^{2\:}-1\right)$$

$$-\frac{36}{5}\left(\frac{10}{9}-\frac{5}{6}\right)$$

$$x\left(1+y^2\right)^{\frac{1}{2}}dx=y\left(1+y^2\right)^{\frac{1}{2}}dy$$

$$\left(x-5y-12\right)^2$$

$$-4\left(x^2-3\right)$$

$$8a-2a+3a$$