9514 1404 393
Answer:
an extraneous solution
Explanation:
A solution that shows up as a result of the process of solving an equation, but that does not work in the original equation, is called "an extraneous solution".
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Additional comment
Radical and rational expression equations can have extraneous solutions. For radical equations, they are typically ones that require a negative square root (or negative root of even index). For rational expression equations, they typically involve "excluded" values, values that make a denominator be zero.