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A-level maths help :(

I have done all the other parts but I am so confused about what to do on part d) of the question. So any help would be much appreciated!
(edited 11 months ago)
Reply 1
Hey! I believe its because as t tends to infinity, the expression tends to 800/3. This is 266.6666... so the value can never reach 270.
Reply 2
Original post by Marvel_fan
Hey! I believe its because as t tends to infinity, the expression tends to 800/3. This is 266.6666... so the value can never reach 270.


Hello, I do get that but wouldn't that mean the denominator would be 4?
Reply 3
Original post by skyeforster15
Hello, I do get that but wouldn't that mean the denominator would be 4?


So what i would do is in the fraction divide each term by e^0.1t
After doing that, since the e^0.1t tends to infinity as t increases, the 1/ (e^0.1t) term you're left with must tend to 0. That means you only have 3 left at the bottom.
Did that make sense, cause i'm not sure if it did! otherwise I can try explain it again :smile:
(edited 11 months ago)
Reply 4
Original post by Marvel_fan
So what i would do is in the fraction divide each term by e^0.1t
After doing that, since the e^0.1t tends to infinity as t increases, the 1/ (e^0.1t) term you're left with must tend to 0. That means you only have 3 left at the bottom.
Did that make sense, cause i'm not sure if it did! otherwise I can try explain it again :smile:


That makes a lot more sense, thank you! :smile:
Reply 5
Original post by skyeforster15
That makes a lot more sense, thank you! :smile:


Happy to help!
Reply 6
Original post by Marvel_fan
Hey! I believe its because as t tends to infinity, the expression tends to 800/3. This is 266.6666... so the value can never reach 270.

You need to be careful with that argument. Just because it tends to 800/3 at infinity doesn't mean there can't be a value "before infinity" where it does hit 270.
Original post by Marvel_fan
So what i would do is in the fraction divide each term by e^0.1t
After doing that, since the e^0.1t tends to infinity as t increases, the 1/ (e^0.1t) term you're left with must tend to 0. That means you only have 3 left at the bottom.
Did that make sense, cause i'm not sure if it did! otherwise I can try explain it again :smile:


Original post by skyeforster15
That makes a lot more sense, thank you! :smile:

You can actually solve directly by setting P = 270 and rearranging. You will end up with the conclusion that e0.1t<0e^{0.1t} < 0 which is a contradiction because e^x can never be negative for any real number x :smile:
Reply 7
Original post by davros
You need to be careful with that argument. Just because it tends to 800/3 at infinity doesn't mean there can't be a value "before infinity" where it does hit 270.



You can actually solve directly by setting P = 270 and rearranging. You will end up with the conclusion that e0.1t<0e^{0.1t} < 0 which is a contradiction because e^x can never be negative for any real number x :smile:


Yes, Thank you that also makes a lot of sense as well.

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