College Algebra / Unit 3 Alg 161 short lesson, about 20 seconds
The Kept-Sign Error
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The idea
The kept-sign error divides an inequality by a negative number without reversing the symbol; the answer set points the wrong way.
In practice
From −2x < 6, the error writes x < −3. Test x = −4: −2(−4) = 8, and 8 < 6 is false — the error's own example fails it.
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