If (x+y)^2 = 100 and (x-y)^2 = 16, find xy.
A12
B16
C21
D24
Explanation
4xy = (x+y)^2 – (x-y)^2 = 100 – 16 = 84 => xy = 21.
Exam Relevance
- Topic: Algebra
- Subtopic: Identities
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