先化简再求值:x⼀y(x+y) -y⼀x(x+y)其中x=(根号2)+1,y=(根号2)-1

2025-02-26 23:17:39
推荐回答(2个)
回答1:

解:
原式=x²/[xy(x+y)]-y²/[xy(x+y)]
=(x²-y²)/[xy(x+y)]
=(x+y)/(x-y)/[xy(x+y)]
=(x-y)/(xy)
=[(√2+1)-(√2-1)]/[(√2+1)(√2-1)]
=(√2+1-√2+1)/(√2²-1²)
=2/(2-1)
=2

回答2:

先把左边的式子上下同乘x,右边的上下同乘y。得到分母相同的式子,同分母分数可以相加减。然后得到分子为:x方-y方分母为:xy(x+y)。运用平方差公式:x方-y方=(x+y)(x-y)。上下约分:x-y/xy。代入x,y的值,得到答案为2