七年级数学下册第1章整式的乘除1.4整数的乘法1.4.2单项式乘多项式精练（新版）北师大版.docx

第2课时单项式乘多项式测试时间:25分钟一、选择题1.化简x(x2+3)+x2(x-3)-3x(x2-x-1)的结果为()A.-x3+6xB.-x3-6xC.-x3-6x2+6xD.-x3-6x21.答案A原式=x3+3x+x3-3x2-3x3+3x2+3x=-x3+6x.2.计算-2a(a2-1)的结果是()A.-2a3-2aB.-2a3+aC.-2a3+2aD.-a3+2a2.答案C3.下列计算结果正确的是()A.(6ab2-4a2b)3ab=18ab2-12a2bB.(-x)(2x+x2-1)=-x3-2x2+1C.(-3x2y)(-2xy+3yz-1)=6x3y2-9x2y2z2+3x2yD.34a3-12b2ab=32a4b-ab23.答案DA.(6ab2-4a2b)3ab=18a2b3-12a3b2,此选项计算错误;B.(-x)(2x+x2-1)=-x3-2x2+x,此选项计算错误;C.(-3x2y)(-2xy+3yz-1)=6x3y2-9x2y2z+3x2y,此选项计算错误;D.34a3-12b2ab=32a4b-ab2,此选项计算正确.故选D.4.要使(-6x3)(x2+ax+5)+3x4的结果中不含x4项,则a的值是()A.0B.12C.-12D.24.答案B原式=-6x5-6ax4-30x3+3x4=-6x5+(3-6a)x4-30x3,由(-6x3)(x2+ax+5)+3x4的结果中不含x4项,得3-6a=0,解得a=12,故选B.5.计算(-3x)(2x2-5x-1)的结果是()A.-6x3-15x2-3xB.-6x3+15x2+3xC.-6x3+15x2D.-6x3+15x2-15.答案B(-3x)(2x2-5x-1)=-3x2x2+3x5x+3x=-6x3+15x2+3x.故选B.6.化简x(2x-1)-x2(2-x)的结果是()A.-x3-xB.x3-xC.-x2-1D.x3-16.答案B原式=2x2-x-2x2+x3=x3-x,故选B.7.下列计算正确的是()A.(-4x)(2x2+3x-1)=-8x3-12x2-4xB.(6xy2-4x2y)3xy=6xy2-12x3y2C.(-x)(2x+x2-1)=-x3-2x2+1D.(-3x2y)(-2xy+3yz+1)=6x3y2-9x2y2z-3x2y7.答案D(-4x)(2x2+3x-1)=-8x3-12x2+4x,A错误;(6xy2-4x2y)3xy=18x2y3-12x3y2,B错误;(-x)(2x+x2-1)=-x3-2x2+x,C错误;(-3x2y)(-2xy+3yz+1)=6x3y2-9x2y2z-3x2y,D正确.故选D.8.要使(y2-ky+2y)(-y)的展开式中不含y2项,则k的值为()A.-2B.0C.2D.38.答案C(y2-ky+2y)(-y)=-y3+ky2-2y2,展开式中不含y2项,k-2=0,解得k=2.故选C.9.已知xy2=-2,则-xy(x2y5-xy3-y)的值为()A.2B.6C.10D.149.答案Cxy2=-2,-xy(x2y5-xy3-y)=-x3y6+x2y4+xy2=-(xy2)3+(xy2)2+xy2=-(-2)3+(-2)2+(-2)=8+4-2=10,故选C.二、填空题10.计算:a(a+1)=.10.答案a2+a解析a(a+1)=aa+a1=a2+a.11.计算:(-2a)14a3-1=.11.答案-12a4+2a解析(-2a)14a3-1=(-2a)14a3+(-2a)(-1)=-12a4+2a.12.计算:12b2-4a2(-4ab)=. 12.答案-2ab3+16a3b解析原式=-2ab3+16a3b.13.计算:12m2n3-2mn2+(2m2n)2=. 13.答案-m3n5+2m6n5解析12m2n3-2mn2+(2m2n)2=12m2n3(-2mn2+4m4n2)=-m3n5+2m6n5.14.已知一圆柱体的底面半径为x,高为2x+4,则它的体积为(结果保留).14.答案2x3+4x2解析圆柱体的体积为x2(2x+4)=2x3+4x2.15.一个长方体的长为2m,宽为3n,高为4mn-1,则这个长方体的体积是.15.答案24m2n2-6mn解析一个长方体的长为2m,宽为3n,高为4mn-1,这个长方体的体积是2m3n(4mn-1)=6mn(4mn-1)=24m2n2-6mn.16.下面规定一种运算:ab=a(a-b),则x2yxy2的计算结果是.16.答案x4y2-x3y3解析ab=a(a-b),x2yxy2=x2y(x2y-xy2)=x4y2-x3y3.17.若-2x2y(-xmy+3xy3)=2x5y2-6x3yn,则m=,n=.17.答案3;4解析-2x2y(-xmy+3xy3)=2xm+2y2-6x3y4=2x5y2-6x3yn,m+2=5,n=4,m=3,n=4.三、解答题18.先化简,再求值:3a(2a2-4a+3)-2a2(3a+4),其中a=-2.18.解析3a(2a2-4a+3)-2a2(3a+4)=6a3-12a2+9a-6a3-8a2=-20a2+9a,当a=-2时,原式=-20(-2)2+9(-2)=-98.19.计算:(1)-43ab292a2b-12ab+34b2;(2)a2