$\left(x\:-7\right)^2\:+\:y\:^2=\:45$

$2x^2-12x$

$\frac{\left(\left(t+n\right)^2-2r^2\right)}{\left(\left(t+n\right)^2-2r\right)}$

$6x^4-15a^3+21x^2$

$f\left(x\right)=\frac{3}{x^3}-\frac{4}{x^2}+\frac{1}{x^7}$

$\lim_{x\to0}\left(\frac{\left(x^2-4\right)^2-16}{x^2}\right)$

$\sec\left(x\right)-\cos^2\left(x\right)$