(xy-1)²+(x+y-2xy)(x+y-2)分解因式用换元法

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(xy-1)²+(x+y-2xy)(x+y-2)分解因式用换元法

(xy-1)²+(x+y-2xy)(x+y-2)分解因式用换元法
(xy-1)²+(x+y-2xy)(x+y-2)分解因式用换元法

(xy-1)²+(x+y-2xy)(x+y-2)分解因式用换元法
令a=x+y-2xy
b=x+y-2
b-a=2xy-2=2(xy-1)
所以原式=[(b-a)/2]²+ab
=(b²-2ab+b²+4ab)/4
=(a²+2ab+b²)/4
=(a+b)²/4
=(2x+2y-2xy-2)²/4
=(xy-x-y+1)²
=(x-1)²(y-1)²

令x+y=a,xy=b
原式化为:
(b-1)^2+(a-2b)(a-2)
=b^2-2b+1+a^2-2a-2ab+4b
=b^2+2b+1+a^2-2a-2ab
=(a^2-2ab+b^2)+2(b-a)+1
=(b-a)^2+2(b-a)+1
=(b-a+1)^2
=(xy-x-y+1)^2
=(x-1)^2(y-1)^2