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A rational expression is an algebraic expression made up of ratios (fractions) of polynomials. It can be written as P(x)/Q(x), where P(x) and Q(x) are polynomial expressions and Q(x) cannot equal zero.
The top part of a fraction in a rational expression. It represents what is being divided.
The bottom part of a fraction in a rational expression. It represents what is doing the dividing.
Simplifying: The process of reducing a rational expression to its simplest form by canceling common factors between the numerator and denominator.