Answer:
If the same number is being added to y, then the function has a constant change and is linear. If the y value is increasing or decreasing by a certain percent, then the function is exponential.
Explanation:
I'll give you an example:
We have 2 functions as tables.
The first table:
X. Y.
1 6
2 9
3 1
4 40
And the second table:
X. Y.
1 2
2 4
3 6
4 8
Which one is linear, and which one is exponential?
The first table is exponential, while the second table is linear.
Why?
The first table's difference of Y1 & Y2 is 3, Y2 & Y3 is 8, Y3 & Y4 is 39. This means that Y does not increase at a constant rate, as X increses by 1. Therefore, this function is exponential.
The second table's difference between Y1 & Y2, Y2 & Y3, Y3 & Y4 is 2. Therefore, 2 is Y's constant change. Since the second table has a constant change, this function is linear.