x1998 =y1999 =z2000 =t=x−z1998−2000 =x−y1998−1999 =y−z1999−2000 .
Hay: x−z−2 =x−y−1 =y−z−1 ⇒x−z=2(x−y)=2(y−z)(1)
(x−z)3=(x−z)2(x−z)=(2(x−y))2(2(y−z))
⇔(x−z)3=8(x−y)2(y−z)ĐPCM a)
x1998=y1999 =z2000 =t = x - z1998 - 2000 = x- z1998 - 2000
Hay
x - z - 2 = x -y -1 = y -z - 1 suy ra x - 2 = 2.( x - y ) = 2.(y - z) suy ra ( x - 2 ) .3 = 8 .( x-y).2.(y -z )