We will be discussing how to perform arithmetic operations on what are called rational expressions.
Each of the following are examples of rational expressions:
\begin{align}\frac{x^2+2x+5}{x+1}&, & \frac{-5x^4-3x+6}{3.14x^2+5.6x-3} &, &\frac{x-1}{\frac{1}{2}x^2-5x+\frac{2}{3}}\end{align}
It is also worth noting that any polynomial is also technically a rational expression, because you can always write a 1 in the denominator, and constants (numbers) are polynomials. For example,
\begin{align}5x^2+3x-2&=\frac{5x^2+3x-2}{1}\end{align}
Throughout the following topics, it helps to keep in mind that, since variables like x represent unknown numbers, polynomials are therefore also unknown numbers (for instance, if I knew what x was in the expression above, then I would be able to figure out the value of 5x^2+3x-2). Thus, all arithmetic performed involving rational expressions mirrors exactly how arithmetic is performed on fractions of numbers.