Expressions and equations
An expression represents a value; an equation states that two expressions are equal. A variable stands for a number that may change or needs to be found.
2x + 5 is an expression. 2x + 5 = 11 is an equation.
Evaluate an expression
Substitute a value for each variable, then follow the order of operations. Use brackets when substituting a negative value.
If x = −3, then x² + 2x = (−3)² + 2(−3) = 3.
Simplify like terms
Combine matching variable parts and keep unlike terms separate.
4x + 3y − x + 2y = 3x + 5y.