=xy(x²+2xy+y²）=xy*(x+y)²=3/2*16=24已知(x+y)²=25,(x-y)²=9,求xy与x²+y²的值展开啊，姐姐（x+y)²=x²+2xy+y²=25（x-y)²=x²-2xy+y²=9上面给2个等式相加，2（x²+y²）=34，（x²+y²）=17上面给2个等式相减，4xy=16，xy=4