2x+y=m+1 (1)x+4y=2m+3 (2)(2)*2-(1)得7y=3m+5 y=3/7m+5/7(1)*4-(2)得7x=2m+1 x=2/7m+1/7令x＞0,y＞0得2/7m+1/7＞0,即m＞-1/23/7m+5/7＞0,即m＞-5/3所以当m＞-1/2时,方程组{2x+y=m+1 x+4y=2m+3}的解是正数...