That is to say:
Run at least 400 meters.
Assuming that the fuse is at least x meters long, it can prove the safety of the operator.
The emergency situation is that the operator just ran 400 meters and the fuse of X meters blew.
The time to blow the fuse is the same as the time for the operator to run 400 meters.
Column equation: x/0.0 12=400/5.
The solution is x = 0.96m m.
So the fuse must be more than 0.96 meters to ensure the safety of the operator?
2, let 5-3x=0, and get x=5/3.
The result can be verified. If x=4 (greater than 5/3) is brought into the equation, the result will be negative, and if x= 1 (less than 5/3) is brought into the equation, the result will be positive. So get the result.
Results:
X & gt5/3, the value of algebraic expression 5-3x is negative.
When x=5/3, the value of algebraic expression 5-3x is 0.
When x< is 5/3, the value of algebraic expression 5-3x is positive.
Okay？ solve