反比例函数y＝2/x过点（a，b），如果a2+b2＝4，a+b＝??

反比例函数Y=2/X过点(a,b),则有b=2/a,即ab=2````````````(1)
又因a^2+b^2=4````````````````````````````````````````(2)

由(1)*2+(2),得a^2+2ab+b^2=8,即(a+b)^2=8````````````````(3)

解(3)式,得a+b=正负二根号二

a+b=2根号2
过程:把a,b代入函数可知ab=2
又知道a^2+b^2=4
所以(a+b)^2=a^2+b^2+2ab=4+2*2=8

a2 b2什么意思？