．若两个整数x,y使x2+xy+y2能被9整除,证明：x和y能被3整除

若两个整数x,y使x2+xy+y2能被9整除,证明：x和y能被3整除． ．若两个整数x,y使x2+xy+y2能被9整除,证明：x和y能被3整除 x.y是整数,且5x-y能被3整除,求证10x2+23xy-5y2能被9整除 (x-y)(x2+xy+y2) (x+y)(x2-xy+y2) 求方程7（x+y）=3（x2-xy+y2）的整数解． 整数x,y满足x2-y2=2xy,求x-y/x+y的值 因式分解x2+y2-xy-x-y+1 x2-4y2-3xy+y+x 若X2+Y2-2X-6Y+10=0 ,求（x2-y2)/xy的值 求方程x+y=x2-xy+y2的整数解拜托耐心讲解下. 满足方程x2+y2=2（x+y）+xy的所有整数解有几对 (x-y)(x2+xy+y2)-xy(y-x) 若2x+y=0则(x2+xy+y2)/(2xy-x2)的值 求证:(x2-xy+y2)3+(x2+xy+y2)3能被2x2+2y2整除 若x-y/x+y=2,则x2+2xy+y2/4xy=多少 4x2-y2/x2-2xy+y2 +(2x-y)/2x2-2xy 若x/y=2,求x2-2xy-3y2/x2-6xy-7y2的值