已知x=√2+√5y=√5-√2求x²+xy=y²和（x+y）²-（x-y）²的值是x²+xy+y²

已知x=√2+√5y=√5-√2求x²+xy=y²和（x+y）²-（x-y）²的值是x²+xy+y²
已知x=√2+√5y=√5-√2求x²+xy=y²和（x+y）²-（x-y）²的值
是x²+xy+y²

已知x=√2+√5y=√5-√2求x²+xy=y²和（x+y）²-（x-y）²的值是x²+xy+y²
x²+xy+y²
=(√2+√5)²+(√2+√5)(√5-√2)+(√5-√2)²
=(√2+√5)²+2(√2+√5)(√5-√2)+(√5-√2)²-(√2+√5)(√5-√2)
=[(√2+√5)+(√5-√2)]²-(√5+√2)(√5-√2)
=(2√5)²-2√5
=20-2√5
(x+y)²-(x-y)²
=[(√2+√5)+(√5-√2)]²-[(√2+√5)-(√5-√2)]²
=(2√5)²-(2√2)²
=20-8
=12