21431xx()2212232ababab()解(1)原式=224341xxx22434xxx32124xx(2)原式=22112322abababab232213abab计算巩固练习:1、计算:(1)3a(5a-2b)(2)(x-3y)·(-6x)2、化简:x(x-1)+2x(x+1)-3x(2x-5)1、解(1)3a(5a-2b)=3a·5a+3a·(-2b)=15a-6ab222222615316xxxxxxxx(2)(x-3y)·(-6x)=x·(-6x)+(-3y)·(-6x)=-6x+18xy2、解:原式=提高练习:22213221xxxxxx1、解不等式:2222223221xxxxxx14x41x解:2、已知22533()ababababb,求的值.36242ababab253()abababb将展开,得解:32222ababab2323333ab将代入,得=27-9-3=15提高练习: