Question

几道数学题 30分钟，急！！！

(1)a^2-4/a+2÷(a-2)x1/a-2

(2)x^2/x-2-x-2

(3)(a+2/x-x+1/x-2)÷x+4/x^2-2x
第三题写错了是：
{1+(2)/(x)-(x+1)/(x-2)}÷(x+4)/(x^2-2x)

Answer 1

解1题：
原式=2xy/(x²-y²)+x/(x+y)
=2xy/[(x+y)(x-y)]+[x(x-y)]/[(x+y)(x-y)]
=[2xy+x(x-y)]/[(x+y)(x-y)]
=(2xy+x²-xy)/[(x+y)(x-y)]
=(x²+xy)/[(x+y)(x-y)]
=[x(x+y)]/(x+y)(x-y)]
=x/(x-y)

解2题：
原式=[a²/(a-2)-4/(a-2)]×[1/(a²+2a)]×(a²+2a)
=[(a²-4)/(a-2)]
=[(a+2)(a-2)]/(a-2)
=a+2

解3题：
原式=[1+3/(x-1)]÷[(x+2)/(x²-1)]
=[(x-1+3)/(x-1)]×[(x²-1)/(x+2)]
=[(x+2)/(x-1)]×[(x+1)(x-1)/(x+2)]
=x+1

Answer 2

(1)、[（a^2-4）/（a+2）]÷[(a-2)x1/（a-2）]
=[（a+2）(a-2)/（a+2）]÷1
=a-2；
(2)、x^2/x-2-x-2=x-2-x-2=-4；

(3)、[(a+2）/x-（x+1）/（x-2)]÷(x+4)/(x^2-2x)
=(ax+x-x^2-2a-4）/（x+4）。

Answer 3

(1)、[（a^2-4）/（a+2）]÷[(a-2)x1/（a-2）]
=[（a+2）(a-2)/（a+2）]÷1
=a-2；
(2)、x^2/x-2-x-2=x-2-x-2=-4；

(3)、{1+(2)/(x)-(x+1)/(x-2)}÷(x+4)/(x^2-2x)
=[(x+2）/x-（x+1）/（x-2)]÷(x+4)/(x^2-2x)
=[(x+2）（x-2）-x（x+1）]/（x+4）
=-1。

Answer 4

(1)、[（a^2-4）/（a+2）]÷[(a-2)x1/（a-2）]
=[（a+2）(a-2)/（a+2）]÷1
=a-2；
(2)、x^2/x-2-x-2=x-2-x-2=-4；

(3)、{1+(2)/(x)-(x+1)/(x-2)}÷(x+4)/(x^2-2x)
=[(x+2）/x-（x+1）/（x-2)]÷(x+4)/(x^2-2x)
=[(x+2）（x-2）-x（x+1）]/（x+4）
=-1。

Answer 5

加上必要的括号啊
1.a-2
2.x^2/-4
3.(a+2)x/(x+4)