Rational expressions

Grade 8 topic of the subject «Mathematics»: Algebra, Chapter I «Rational fractions», § 1 «Rational expressions» (pp. 4–7). Integer expressions are built from numbers and variables using addition, subtraction, multiplication and division by a non-zero number. Expressions that contain division by an expression with a variable are called fractional. Integer and fractional expressions are called rational expressions. A fraction whose numerator and denominator are both polynomials is a rational fraction. The values of the variable that do not make the denominator zero are its permissible values.