Brainliest + points

can someone ?

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

If you double the input of a function and it results in half the output, and if you triple the input and it results in a third of the output, what can be guessed about the function? check all that apply.

The sum of the speeds of two trains is 720.2 mph. if the speed of the first train is 7.8 mph faster than the second train, find the speeds of each.