1、第8章 整式乘法与因式分解,8.1 幂的运算,知识点1 同底数幂的除法1.计算( -a )4( -a )的结果是( C ) A.a5 B.a4 C.-a3 D.a3 2.计算: ( 1 )( -x )8( -x )5;( 2 )( -2 )201922018;( 3 )( x-y )10( x-y )3.,解:原式=( -x )3=-x3.解:原式=-2201922018=-2.解:原式=( x-y )10-3=( x-y )7.,5.下列计算正确的是( D ) A.a2+a3=a5 B.a2a3=a6 C.( a2 )3=a5 D.a5a2=a3 6.计算( a2 )4a5a的结果是( A
2、) A.a2 B.a3 C.a4 D.a5 7.已知10m=20,10n=0.2,则m-n的值为( B ) A.1 B.2 C.-4 D.-2 8.已知3a-2b-3=0,则53a52b= 125 . 【变式拓展】若2a-b-5=0,则22a2b4= 8 . 9.计算:( -x2y )6( -x2y )3= -x6y3 .,10.计算: ( 1 )( -2x3 )2( x5x2 );( 2 )( x-y )13( y-x )5( x-y ).,解:原式=4x6x3=4x3.解:原式=( x-y )13-( x-y )5( x-y )=-( x-y )13-5-1=-( x-y )7.,11.已知39m27m=321,求( -m2 )3( m3m2 )的值.,解:39m27m=332m33m=31+5m=321, 1+5m=21,解得m=4, ( -m2 )3( m3m2 )=-m6m5=-m=-4.,12.已知x3n-2xn+1=x3-nxn+2,求n的值.,解:x3n-2xn+1=x3n-2-n-1=x2n-3, x3-nxn+2=x3-n+n+2=x5, x2n-3=x5,2n-3=5,解得n=4.,
