2017年中考数学分式化简备考练习及答案
来源 :中华考试网 2016-10-25
中参考答案
1.C 2.D 3.B 4.7z36x2y x+3x+1 5.32 6.-1
7.解:原式=x+4+x-4x+4x-4•x+4x-42
=x+4+x-42=x.
8.解:原式=x2-1x-1=x+1,当x=2时,原式=3(除x=1外的任何实数都可以).
9.解:原式=m-22m+1m-1•m-1m-2+2m-1=m-2m+1+2m-1=m-2m-1+2m+1m+1m-1=m2-m+4m+1m-1,
当m=2时,原式=4-2+43=2.
10.m-6 11.1
12.解:原式=1a+1-a+2a+1a-1•a-12a+1a+2=1a+1-a-1a+12=2a+12,
∵a2+2a-15=0,∴(a+1)2=16.
∴原式=216=18.
13.-4 解析:由xyx+y=-2,得x+yxy=-12,裂项得1y+1x=-12.同理1z+1y=43,1x+1z=-43.所以1y+1x+1z+1y+1x+1z=-12+43-43=-12,1z+1y+1x=-14.于是xy+yz+zxxyz=1z+1y+1x=
-14,所以xyzxy+yz+zx=-4.
14.解:原式=ab+1b+1b-1+b-1b-12=ab-1+1b-1=a+1b-1.
由b-2+36a2+b2-12ab=0,得b-2+(6a-b)2=0,
∴b=2,6a=b,即a=13,b=2.
∴原式=13+12-1=43.