英语.都好的进来!1.轮船在静水中航行每小时走x千米,水流速度为y千米/时,则轮船逆水航行50千米用_____小时.2.
1个回答

船逆水的时速是x-y,行驶50公里用时50/(x-y)

x^2+3x+1=0,x^2+1=3x,x+1/x=3,(x+1/x)^2=x^2+1/x^2+2=9,x^2+1/x^2=7

原价*(1+0.3)*(1-0.7)=原价*0.39=a,原价=a/(0.39)=100a/39

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