16.1二次根式(2).的式子叫做二次根式形如a)0(a二次根式的定义:二次根式的性质:0,0.aa(双重非负性)复习回忆2)4(2(9)2(16)2)0(aa2(a≥0)04916例2:计算222(1)(1.5)(2)(25)(3)(33)练习1:用心算一算:2512233518242322204320aa2(a≥0)2)4(2(3)2-2432aa2(a<0)aa2(a≥0)aa2(a<0)aa2a-a(a≥0)(a<0)例3:化简2225)4()5()3()5()2(16)1(222210.4.371.23.0.1:.1计算练习:练习2:2yx2211122223yxyx(xy)﹤xy212x(x>0)1x?)(22有区别吗与aa2.从取值范围来看,2a2aa≥0a取任何实数1:从运算顺序来看,2a2a先开方,后平方先平方,后开方3.从运算结果来看:=aa(a≥0)2a2a-a(a<0)==a∣∣化简下列各式:)0,0()4()8(6416)3()5()5()2()32()23)(1(2222222babammm若a.b为实数,且求的值022ba1222bba解:20a,02b022ba而20a,02b22ab,31212212222ba原式22)()(,,,)2(cabcbaABCcba化简的三边长为△已知(2003年·河南省)实数p在数轴上的位置如图所示,化简222)1(pp121)2(1pppp的值。求:互为相反数,与:已知bababa,86