The addition and subtraction of fractions in the second volume of the eighth grade! Only 15 and 16 questions! Where a × a + ab-2b × B = 0 2.a÷〔(a-b)(a-c)〕+b÷〔（b-c)(b-a)〕+c÷〔(c-a)(c-b)〕 3.(2x+z-y)÷(x×x-xy+xz-yz)-(2x+y+z)÷(x×x+xy+xz+yz) 4.1÷(a+1)+1÷(a+1)(a+2)+… +1÷(a+2007)(a+2008) Note: a × A is the square of a and so on, [

1 - A-B because a △ B-B △ a - (a × a + B × b) △ AB = (- 2 × B's Square) / ab
And a × a + ab-2b × B = 0, that is, a (a + b) = the square of 2 × B, that is, the square of 2 × B / a = a + B
So the value of the original formula is - a-b
4 1 / (square of X + 2009 + 2008) it's not easy to say on the computer, but please believe me
My ability is limited

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