1.计算1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)

来源：学生作业帮编辑：神马作文网作业帮分类：数学作业时间：2024/11/17 12:09:46

1.计算1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)
2.若2a-b=0则分式a-b/a+b的值是
3.走一段山路,上坡速度为v1下坡速度为v2则其平均速度为,有四个选项（A.v1+v2/2 B.v1v2/v1+v2 C.2/v1+v2 D.2v1v2/v1+v2）
4.先化简,再求值(a-b/a+b)+(a+b/a-b)-(2a^2-2b^2/a^2+b^2)其中a=-2,b=1/2.

1.1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)
=1/(x-1)-1/x+1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)
=1/(x-1)-1/(x+3)
=(x+3-x+1)/(x-1)(x+3)
=4/(x-1)(x+3)
2.2a-b=0
b=2a
a-b=a-2a=-a
a+b=a+2a=3a
(a-b)/(a+b)=-1/3
3.平均速度是D
4.(a-b/a+b)+(a+b/a-b)-(2a^2-2b^2/a^2+b^2)
=(a-b)/(a+b)+(a+b)/(a-b)-(2a^2-2b^2)/(a^2+b^2)
=[(a-b)^2+(a+b)^2]/(a^2-b^2)-(2a^2-2b^2)/(a^2+b^2)
=(2a^2+2b^2)/(a^2-b^2)-(2a^2-2b^2)/(a^2+b^2)
=[2(a^2+b^2)^2-2(a^2-b^2)^2]/(a^4-b^4)
=8a^2b^2/(a^4-b^4)
ab=-1
=8/(16-1/16)
=8/255/16
=8*16/255
=128/255

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