2根号a^2b^3
跟好有意义则a²b³≥0
所以b≥0
所以原式=2√[(ab)²b]
=2|ab|√b
=2b|a|√b
根号11^2-7^2
=√[(11+7)(11-7)]
=√(18×4)
=√[(3×2)²×2]
=6√2化简2根号a^2b^3做了采纳吧