已知a+b=6,ab=4且a＞b求（√a-√b)/(√a+√b)

Question

已知a+b=6,ab=4且a＞b求（√a-√b)/(√a+√b)

Answer 1

当a+b=6ab+4时原式=根号[（a+b-2根号ab）]/（a+b+2根号ab）]=根号[（6-2根号4）/（6+2根号4）]=根号[（6-2*2）/（6+2*2）]=根号[2/10]=1/5根号5