$\lim_{x\to0}\left(\frac{x^3}{e^{2x}}\right)$

$\left(2a^2b^3+3\right)\left(2a^2b^3-9\right)$

$\frac{\left(3\cdot10^8\right)}{400\cdot10^{-7}}$

$\frac{3}{x-1}=\frac{4}{x+2}$

$3\left(a+b\right)^2c+3\left(a+b\right)c^2$

$\frac{\cos^2d-\sin^2d}{\cos^2d+\sin d\cos d}=\frac{\cot d-1}{\cot d}$

$\tan\theta-1=\frac{\sec\theta-\csc\theta}{\csc\theta}$