初一 数学 因式分解 请详细解答,谢谢! (25 19:22:21)

a2-4a+4-b2
=(a-2)²-b²
=(a+b-2)(a-b-2)

2/1x2-xy+2/1y2
=2/1*(x²-2xy+y²)
=2/1*(x-y)²

(x2-6x)2+17(x2-6x)+72
=(x²-6x+8)(x²-6x+9)
=(x-2)(x-4)(x-3)²

1.
a^2-4a+4-b^2
=(a^2-4a+4)-b^2
=(a-2)^2-b^2
=[(a-2)-b][(a-2)+b]
=(a-2-b)(a-2+b)

2.
(1/2)x^2-xy+(1/2)y^2
=(1/2)(x^2-2xy+y^2)
=(1/2)(x-y)^2
=(x-y)^2/2

3.
(x^2-6x)^2+17(x^2-6x)+72
=[(x^2-6x)+8][(x^2-6x)+9]
=(x^2-6x+8)(x^2-6x+9)
=(x-2)(x-4)(x-3)^2

1,(a-2)^2-b^2=(a-2-b)(a-2+b)
2，1/2（x^2-2xy+y^2)1/2(x-y)^2
3,(x2-6x)2+17(x2-6x)+72=(x^2-6x+8)(x^2-6x+9)

1.=(a-2)²-b²=(a+b-2)*(a-b-2)

2.通分=（x²-2xy+y²）/2=（x-y)²/2

3.=(x2-6x+8)(x2-6x+9) =（x-2）（x-4）（x-3)²