△=(7m+3)²-4(5m+1)×3m
=49m²+42m+9-60m²-12m
=-11m²+30m+9
△≥0时,方程有两个实数根
-11m²+30m+9≥0
11m²-30m-9≤0
(m-3)(11m+3)≤0
(m-3)与(11m+3)异号,有两种情况
m-3≥0 且 11m+3≤0,这时,无解
或 m-3≤0 且 11m+3≥0,解集为 -3/11≤m≤3
所以,当-3/11≤m≤3时,方程有两个实数根