This document summarizes key concepts about polynomials, rational expressions, and functions. It discusses that polynomials are algebraic expressions involving numbers and letters related by addition or subtraction of monomials. It also explains several methods of factorizing polynomials, such as common factor, difference of squares, and perfect square trinomial. The document defines rational expressions as those with variables in the denominator or numerator with integer exponents. It provides four ways to define a function - descriptively, numerically, graphically, and analytically. It explains that the domain is the set of inputs and the image is the set of outputs. Finally, it gives an example of determining the domain of a function f(x)=4-1-2x.