求不定方程X1+2X2+3X3=16满足X1≥1,X2≥-1,X3≥1的整数解的个数
问题描述：
求不定方程X1+2X2+3X3=16满足X1≥1,X2≥-1,X3≥1的整数解的个数
答
用笨办法也不失为好办法：x3=1时,x1+2x2=13,x1=13-2x2,x2=-1,0,1,2,3,4,5,6,共8 个x3=2时,x1+2x2=10,x1=10-2x2,x2=-1,0,1,2,3,4,共6 个x3=3时,x1+2x2=7,x1=7-2x2,x2=-1,0,1,2,3,共5 个x3=4时,x1+2x2=4,x1=4-2x2,x2=-...