Algebra

Solving an Equation but Forgetting to Check the Answer

A student stops after the algebra steps and writes every found value as an answer without substituting it back into the original equation.

Quick check

Why students make it

Solving steps feel reversible, but some moves, such as squaring both sides or multiplying by an expression with a variable, can add extra values. Students may check only whether the algebra looks neat instead of whether the original equation is true.

The rule done right

After solving, substitute each candidate into the original equation. Keep only the values that make the original equation true.

Related resources

equationsextraneous-solutionschecking