1.2/x-3=2/2x-1 2.若la-3l+根号b+1=0,求(a/a-b-b/b-a)÷a+b/ab的值.
问题描述：
1.2/x-3=2/2x-1 2.若la-3l+根号b+1=0,求(a/a-b-b/b-a)÷a+b/ab的值.
3.(3/x-1-x-1)÷x-2/x²-2x+1,其中x=-2
4.x²-4y²/x²-4xy+4y²,其中x=5,y=-7
急.＋赏金!
答
1.2/x-3=2/2x-1
2x-1=x-3
x=-2
经检验,x=-2是原方程的解.
2.若la-3l+根号b+1=0,
a=3,b=-1
则(a/a-b-b/b-a)÷a+b/ab=（a+b)/(a-b)]*（ab/(a+b)=ab/(a-b)=-3/4.
3.(3/x-1-x-1)÷x-2/x²-2x+1
=(3-(x-1)²)((x-1)²]/[(x-2)(x-1)]
=[3-(x-1)²](x-1)/[(x-2)
=(3-9)(-3)/(-4)
=-9/2
其中x=-2
4.x²-4y²/x²-4xy+4y²
=(x+2y)(x-2y)/(x-2y)²
=(x+2y)/(x-2y)
=(-9)/(19)
=-9/19
其中x=5,y=-7