21.2二次根式的乘除(2)VIP专享VIP免费

二次根式的乘除（二）1.什么叫二次根式？叫做二次根式。式子)0(aa2.三个基本性质:知识回顾：=aa(a≥0)2a2a-a(a≤0)==a∣∣(a≥0)≥a___0≥思考：二次根式的除法有没有类似的法则呢？3.二次根式的乘法：abba)0,0(baabba(a≥0,b≥0)94,94.14916,4916.29494491649160,0bababa32327474计算下列各式,观察计算结果,你发现什么规律?3232(3)5252＝＝规律:0,0ba例４：计算1812323241解：83243241222418231812318123293baba331050(2)232)1(计算：10751436152112)4(解：原式)3(原式)4(107514＝710521＝6＝2111526＝23652＝65＝41623223215105010502ba0,0ba例5：化简103100310031解：yxyxyx35925925322ba1631)2(1003)1(＝）（16312注意：如果被开方数是带分数，应先化成假分数。16191619＝419＝29253yx练习：9721)(281(2)025xx1966401690904×.×.)(2216(3)0,0bcaba359259259721＝＝＝）（解：x=x=x)(5925812581222cab=acb=acb=acb)(4416163222211239148013301966401690901966401690904=×.×.=×.×.=×.×.)(abbaabbxx3)23(2)4(82346)3()21()213()2(802)1(35322计算：课堂小结：二次根式的除法法则：0,0babababa0,0baba