射进来吧
幼苗
共回答了22个问题采纳率:95.5% 举报
____________________________________________________________________________________设上、下坡路分别为S,S'km 则从甲到乙所用时间表示为:S/28+S'/42=17/4 (1) S/42+S'/28=14/3 (2) (2)×42-(1)×28 =S'(42/28-28/42)=14×14-17×7=196-119 =S'(42-28)/42×28=77 =S'(42+28)(42-28)/(42×28)=77 =S'70×14/(42×28)=77 得5S'/42=11 S'=42×11/5=462/5 将S’=42×11/5代入(1) S/28+11/5=17/4 解得S=41×28/20=574/10 答:上、下坡路长分别为,574/10km,462/5km ____________________________________________________________________________________
1年前
4