College Algebra / Unit 2 Alg 071 short lesson, about 20 seconds
The Missing-Middle Error
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The idea
The missing-middle error squares a binomial term by term — (a + b)² rewritten as a² + b² — and loses the middle 2ab.
In practice
At a = 1, b = 4: (1 + 4)² is 25, while 1 + 16 is 17. The missing 2ab is the missing 8.
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