根号a-根号a分之一=3√a-1/√a=3(√a-1/√a)²=3²a-2+1/a=9a+1/a=11a+2+1/a=13(√a+1/√a)²=13√a+1/√a=√13根号a+根号a分之一的结果是√13
√a-1/√a=3,(√a+1/√a)^2=(√a-1/√a)^2+4=9+4=13,√a+1/√a>0,∴√a+1/√a=√13.
