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方程2x2-xy-3x+y+2006=0的正整数解(x,y)共有______对.
人气:221 ℃ 时间:2019-09-29 16:06:20
解答
2x2-xy-3x+y+2006=0,
∴-2x2+xy+2x+x-y=2006
∴(2x-2x2)+(xy-y)+(x-1)=2006-1,
∴-2x(x-1)+y(x-1)+(x-1)=2005,
∴(x-1)(y+1-2x)=2005=5×401
当①x-1=1,y+1-2x=2005,
即(x,y)=(2,2008)
当②x-1=5,y+1-2x=401,
即(x,y)=(6,412)
当③x-1=401,y+1-2x=5,
即(x,y)=(402,808)
当④x-1=2005,y+1-2x=1,
即(x,y)=(2006,4012).
故答案为4对
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