Can someone please help

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?

Here is another math questions. i will keep asking different questions. 4^2x=6