>>11781429Just show that the function x/(a + x) is continuous at x = 0.
If you do that, then the limit as x approaches 0 will be the same as just plugging 0 in for x.
However, if x/(a + x) is not continuous at x = 0 (this happens when a = 0), then you can't just plug x = 0 in, and you will have to come up with a different strategy for figuring out the limit.
