5.4 分式的加减(2)——异分母分式的加减-【精彩练习】2023-2024学年七年级下册数学同步评价作业教师用书配套Word（浙教版）

色学科网书城四 品牌书店·知名教辅·正版资源 b2 xxk.c0m● 您身边的互联网+款辅专家 5.4分式的加减(2)—异分母分式的加减（见学生用书P34) 1.化简2mm2一4-1m-2,结果是(C) A.m-2 B.m+2 C.Im+2 D.Im-2 2.若y=x一y,则分式1x一1y=(C) A.Ixy B.y-x C.-1 D.I 3.分式1x2一2x与1x的最简公分母是xc一2) 4.若ab=1,a十b=2,则1a十1b的值为2 【解析】1a+1b=b十aab, 当ab=1,a+b=2时，原式=21=2 5.若x=3y,则4x2一y2-x十xy的值是一12 【解析】原式=4y-(x十y)2(x十y)(x一y)=y-x2-2y-y2(x一y)(x十y)=- (x-y)2(x-y)(x十y=-x-x十y 当x=3y时，原式=一3y-yy+y=-12 6.计算： (1)y3x2-16y. (2加-2x2-2x-4在 (3)1-x2x-6+xx-3.(4x十1x-1-4x2-1. (⑤1x-1+x+1.(6r+1-4x2-1-1 解：(1)原式=2y262y-x62y=2y2-x6r2y (2)原式=x-2x2-x(2x-4)x2=x-2-2x2+42=-2x2-5x+2x2. (3)原式=1-x2(x-3)+2x2(x-3)=1-x+2x2(x-3)=1+x2x-6. (4)原式=(x+1)2(x+1)(x-1)-4(x+1)(x-1)=x2+2x+1-4x(x+1)(x-1) =(x-1)2(x+1)(x-1)=x-Ix+1. (5)原式=1x-1+x2-1x-1=1+x2-1x-1=x2x-1. (6原式=x(-1)(x+1)(x-I)-4(x+1)(-1)-(x+1)(x-1)(x+1)(x-1) =x2-x-4-x2+1(x+1)(x-1)=-x十3x2-1 ·独家授权侵权必究·