baababba知识回顾如果把这个式子反过来,则得到:积的算术平方根(a≥0,b≥0)二次根式的乘法法则:(a≥0,b≥0)两个二次根式相乘,将它们的被开方数相乘的积,作为积的被开方数;例题1:计算)()()(原式解:)()原式()原式()()()()()()()()(练习1:计算ba)(xyxy)(例2计算:baabababxyxyba)(xyxy)(yxyyxyxyxxybaababaxxabaxx)()()()()()(练习2:计算比一比谁最强1.化简:(1)(2)(3)(4)(5)(6)(7)(8)(9)572731155612aba216xxyxyyxxy随堂随堂练习练习随堂随堂练习练习随堂随堂练习练习小结二次根式的乘法法则:0)b0,(aabba两个二次根式相乘,将它们的被开方数相乘的积,作为积的被开方数;化简:(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)23816xyx322399yxyx作业aaxxyBCA例3、如图,在△ABC中,∠C=900,AC=10cm,BC=24cm.求:AB.