Expand Expression: Expand the expression using the distributive property: \(1-x^2)(1-y^2) = 1 - y^2 - x^2 + x^2y^2\.
Add 4xy: Add 4xy to the expanded expression: 1−y2−x2+x2y2+4xy.
Combine Like Terms: Combine like terms if possible. There are no like terms to combine, so the expression remains as is: 1−y2−x2+x2y2+4xy.
Check for Factorization: Check for any possible factorization or simplification. No further simplification is possible, so the final answer is 1−y2−x2+x2y2+4xy.
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