Rational expressions include algebraic expressions and fractions.
Algebraic expressions: Algebraic expressions include monomials and polynomials.
1. Single item: such as 12, a, 12a, 7ab.
2. Polynomials: such as a+b, 2abc+abd, a+b/2.
Two: score: such A+B/Ckloc-0//b, a+b/c.
Irrational number formula: such as root number 2.