中间应该是除号,不然不能这么化的.
(x-y)÷ (√x+√y)
=(√x+√y) (√x-√y) ÷(√x+√y)
=(√x-√y)
x-y=(√x+√y) (√x-√y) 这里用的平方差公式 a²-b²=(a+b)(a-b)
[ (x-y)^3 × (√x+√y)^(-3) + 3(x√y-y√x) ] / (x√x+y√y)=[( (x-y) / (√x+√y))^3 + 3(x√y-y√x) ] / (x√x+y√y)=[ ((√x-√y)(√x+√y)/(√x+√y))^3 + 3(x√y-y√x) ] / (x√x+y√y)=[ (√x-√y)^2 + 3√xy(√x-√y) ] / √xy(√x+√y)= (√x-√y) (√x-√y + 3√xy) / √xy(√x+√y)= (√x-√y) ^2(√x-√y + 3√xy) / √xy(x-y)