化简(x1/2-y1/2)÷(x1/4-y1/4) =1/2(x-y)÷1/4(x-y)=1/2÷1/4=1/2*4=2
（x^1/2-y^1/2)/(x^1/4-y^1/4)=(x^1/4+y^1/4)(x^1/4-y^1/4)/(x^1/4-y^1/4)=x^1/4+y^1/4
