设方程为 x/a+y/b=1 ∵a+b=2 (-2)/a+3/b=1 => 3a-2b=ab=> 3(2-b)-2b=(2-b)*b => b^2-7b+6=0 =>b1=6 ,b2=1=> a1=-4 ,a2=1∴方程 x/(-4)+y/6=1 => 3x-2y+12=0x/1+y/1=1 => x+y=1 为所求 .