2x+3y=20
移項(xiàng),得3y=20-2x
兩邊同除以3,得y=（20-2x）/3
當(dāng)x=0時,y=20/3
當(dāng)x=1時,y=6
當(dāng)x=2時,y=16/3
當(dāng)x=3時,y=14/3
當(dāng)x=4時,y=4
當(dāng)x=5時,y=10/3
當(dāng)x=6時,y=8/3
當(dāng)x=7時,y=2
當(dāng)x=8時,y=4/3
當(dāng)x=9時,y=2/3
當(dāng)x=10時,y=0
故二元一次方程2x+3y=20的非負(fù)整數(shù)解有4對：x=1,y=6；x=4,y=4；x=7,y=2；x=10,y=0.