Question

因式分解（x²＋y²）²－4x²y²？？？

Answer 1

（x²＋y²）²－4x²y²
=x^4+2x²y²+y^4-4x²y²
=x^4-2x²y²+y^4
=(x²-y²)²
=(x+y)²(x-y)²