（1）√4a²b³ =2ab√b
(2)√x^4﹢x²y² =x √(x²+y²)
(3)√3∕100 =√3/10
(4)√25x^4∕9y² =5x²/3y
(5)4√2∕3√7 =4√14/21
(6)2a∕√(a﹢b) =2a√(a+b)/(a+b)