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# Limits question help watch

1. Can someone help me with 3(iv)?
2. Divide through by x as a first step...
3. (Original post by DFranklin)
Divide through by x as a first step...
wouldn't you move ax to the left so that e^x - ax=0, and then differentiate?
thats what I did but I don't know what to do next
4. (Original post by SWISH99)
wouldn't you move ax to the left so that e^x - ax=0, and then differentiate?
No I wouldn't. Why do you think that would help?
5. (Original post by DFranklin)
No I wouldn't. Why do you think that would help?
thats what I did for question ii)
6. (Original post by SWISH99)
thats what I did for question ii)
Yes, and when you did it for (ii), you got e^x - 1, which you deduced was >=0 for x >=0. However, note that e^x - 1 equals 0 when x = 0. So this is already the best you can do using this simple method - if you take then which is < 0 when x = 0.
7. (Original post by DFranklin)
Yes, and when you did it for (ii), you got e^x - 1, which you deduced was >=0 for x >=0. However, note that e^x - 1 equals 0 when x = 0. So this is already the best you can do using this simple method - if you take then which is < 0 when x = 0.
I see what you're saying. So how would dividing by x help?
8. what year are yo in?
9. (Original post by SWISH99)
I see what you're saying. So how would dividing by x help?
Have a think about what "the biggest value s.t. for x >=0" means in terms of the graph of .

(I don't want to spell this out for you, this is the kind of thing you need to get used to understanding on your own).
what year are yo in?
why?
11. (Original post by DFranklin)
Have a think about what "the biggest value s.t. for x >=0" means in terms of the graph of .

(I don't want to spell this out for you, this is the kind of thing you need to get used to understanding on your own).
Oh I think I get what you mean. Differentiating e^x/x in order to find the minimum point?
12. (Original post by SWISH99)
Oh I think I get what you mean. Differentiating e^x/x in order to find the minimum point?
Yes, that's right
13. this is complicated and I'm in year 10 and I'm getting really scared
this is complicated and I'm in year 10 and I'm getting really scared
This is undergrad, you won't have to worry about limits for a while. (the earliest you'll encounter them is probably year 13)
15. oh thank god

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Updated: October 9, 2017
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