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八下 ,
八下 ,

八下 ,
21.
1.-8a(x²-2xy+y²)
=-8a(x-y)²
2.原式=(a²+1+2a)(a²+1-2a)
=(a+1)²(a-1)²
22.
两边同乘以x(x-1),得
6x-3x+3=x+5
2x=2
x=1
经检验x=1是增根,所以方程无解.

1,-8a(x y)2 2.-(a2-1)(3a2 1)

(1)
-8ax^2+16axy-8ay^2
=-8a(x^2-2xy+y^2)
=-8a(x-y)^2
(2)
(a^2+1)^2-4a^2
=a^4-2a^2+1
=(a^2-1)^2
(3)
6/(x-1)-3/x=(x+5)/[x(x-1)]
6x-3(x-1) = (x+5)
2x=2
x=1

21.(1)-8aX^2+16axy-8ay^2
=-8a(x^2-2xy+y^2)
=-a8(x-y)^2
(2)(a^2+1)^2-4a^2
=(a^2+1+2a)(a^2+1-2a)
=(a+1)^2(a-1)^2
22. 6/(x-1)-3/x=(x+5)/x(x-1)
6x-3(x-1)=x+5
2x=2
x=1
因为当x=1时x-1=0
所以方程无解(分母不能为0)

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