Question

八年级下册数学分解因式

1.x²-y²-3x-3y
2.1-(a-b)/(a+2b)÷（a²-b²)/(a²+4ab+4b²）
3.4/(x-2)-x+2
请写出解题过程。

Answer 1

(1),x^2-y^2-3x-3y
=(x+y)(x-y)-3(x+y)
=(x+y)(x-y-3)
(2),1-(a-b)/(a+2b)÷(a^2-b^2)/(a^2+4ab+4b^2)
=1-(a-b)/(a+2b)×(a^2+4ab+4b^2)/(a^2-b^2)
=1-(a-b)/(a+2b)×(a+2b)^2/[(a+b)(a-b)]
=1-(a+2b)/(a+b)
=-b/(a+b)
(3),4/(x-2)-x+2
=[4+(-x+2)(x-2)]/(x-2)
=(4-x^2+4x-4)/(x-2)
=x(4-x)/(x-2)

Answer 2

1： (x+y)(x-y)-3(x+y)=(x+y)(x-y-3)
2: 1-(a-b)/a+2b*(a+2b)2/(a+b)(a-b)=1-(a+2b)/(a+b)=-b/a+b
3: 4/(x-2)-x+2=4/(x-2)-(x-2)2/(x-2)=（x+2)(-x+6)/(x-2)
回答完毕！

Answer 3

解答：
1.x²-y²-3x-3y=(x+y)(x-y)-3(x+y)=(x+y)(x-y-3)
2.1-(a-b)/(a+2b)÷（a²-b²)/(a²+4ab+4b²）
=1-(a-b)/(a+2b)*(a+2b)^2/(a+b)(a-b)=1-(a+2b)/(a+b)=-b/(a+b)
3.4/(x-2)-x+2=[4-(x-2)^2]/(x-2)=-(x^2-4x)/(x-2)

Answer 4

1.=(x-y)(x+y)-3(x+y)
=(x-y-3)(x+y)