FORMULABANK

Most of the rules for solving equations also apply to solving inequalities.

This means you can…

• Multiply
• Divide
• Add
• Subtract

...by the same number on both sides (except 0).

However, keep in mind that:

• If you multiply or divide by a negative number, you must "reverse the inequality sign."
  • This means ">" becomes "<" and "<" becomes ">".
  • Example: "5 < x" becomes "-5 > -x" when multiplied by "-1".
• You cannot swap the left and right sides as you do with equations.
  • Example: "x = 5" is the same as "5 = x".
  • However, "x < 5" is NOT the same as "5 < x".
• Often, the solution to an inequality is a set of numbers.
  • Therefore, the solution is often expressed as an interval.
  • Example: The solution to "5 < x" is ]5; ∞[.