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The identity (a + b)(a − b) equals:

Aa² + b²
Ba² − b²
Ca² + 2ab + b²
D2ab
Answer & Solution
Correct answer: B. a² − b²
(a + b)(a − b) = a² − ab + ba − b² = a² − b². The cross terms cancel. This 'difference of squares' identity is one of the most useful in factorisation.
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