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Glossary

Equation

Expression or equation

An equation is a statement that two expressions are equal, for example \(3x - 4 = 11\). A solution of the equation is a value of the variable that makes the statement true.

  • Balance. An equation still holds when you add the same number to both sides or subtract it from both sides, or when you multiply or divide both sides by the same non-zero number.
  • Linear equation. The variable appears only to the first power. An equation like this usually has exactly one solution.
  • Checking. Substitute the solution into the original equation: the two sides must be equal.

Examples

  1. E1

    Solve \(4x + 7 = x - 8\).

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    Subtract \(x\) from both sides: \(3x + 7 = -8\). Subtract 7: \(3x = -15\). Divide by 3: \(x = -5\).

    Check: \(4 \cdot (-5) + 7 = -13\) and \(-5 - 8 = -13\).

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