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# AQA A2 Mathematics MPC4 Core 4 - 9th June 2015 [Discussion & unofficial markscheme] watch

1. (Original post by CD223)

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It's going alright, I'm nearing the end of doing all the core 3 papers for a second time but I just can't get the hang of differential equations! Like I can solve them easily but it's he informationy ones that get me haha! Got a week and gonna go hard core lol, how about you?
2. (Original post by Baloney26)
It's going alright, I'm nearing the end of doing all the core 3 papers for a second time but I just can't get the hang of differential equations! Like I can solve them easily but it's he informationy ones that get me haha! Got a week and gonna go hard core lol, how about you?
Haha yeah I know what you mean. Weirdly M2 has helped with differential equations!

I'm gonna focus entirely on the exams I have between the 5th and 11th over the next week!

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3. (Original post by CD223)
Haha yeah I know what you mean. Weirdly M2 has helped with differential equations!

I'm gonna focus entirely on the exams I have between the 5th and 11th over the next week!

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Agree with the M2 thing
4. Can someone help of part 4bii, always kept getting it wrong.

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5. When t = T the growing colony is 45000 more than the dying colony. So (at T): growing colony - dying colony = 45000

=> 500e^(T/8) - 500000e^(-T/8) - 45000 = 0

=> e^(T/8) - 1000e^(-T/8) - 90 = 0

Think about how you can make this into a quadratic and then solve. Remeber that some solutions might not be valid (depending on what variable your quadratic is in). Hope this helps. Didn't want to give it all away!
6. Can someone help me with the very last question on Jan 13 MPC4.

You have to determine when dN/dt is a maximum value.

This is like determining when the gradient of a line is a maximum. How is that done? taking the second derivative would enable you to determine whether stationary points are a maximum or a minimum.. But this is when the gradient is zero, not a maximum. So why would the second derivative help?

Any help?

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7. (Original post by Jimmy20002012)
Can someone help of part 4bii, always kept getting it wrong.

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I literally done this question yesterday, I actually loved this question, I could show you my solution if you want?

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8. (Original post by JF2013)
I literally done this question yesterday, I actually loved this question, I could show you my solution if you want?

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Yeah I quite liked it till the last part. Could solve the equation and everything, it's just forming it kinda getting know where with it. Would be much appreciated

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9. (Original post by Jimmy20002012)
Can someone help of part 4bii, always kept getting it wrong.

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10. Thanks. Just to make sure I understand what you have initially done, is this right. Using the app again haha.

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11. (Original post by Jimmy20002012)
Thanks. Just to make sure I understand what you have initially done, is this right. Using the app again haha.

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Yeah - you're setting P equal to Q, but only when P is greater by 45,000

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12. (Original post by CD223)
Just purely past papers! How about you?

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just done my first paper.

in june 2010, I struggled on 6aii, and 6bii?
confused on how to use the information given

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Attached Images

13. (Original post by the_googly)
just done my first paper.

in june 2010, I struggled on 6aii, and 6bii?
confused on how to use the information given

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Does this help?

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14. (Original post by CD223)
Does this help?

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thanks a lot! have you come across any similar questions like this?

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15. (Original post by the_googly)
thanks a lot! have you come across any similar questions like this?

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Yeah they come up fairly often. Not every paper but certainly every couple of years

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16. (Original post by CD223)
Yeah they come up fairly often. Not every paper but certainly every couple of years

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ill be prepared for the next one then!

couldn't get my head around 9bii also

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Attached Images

17. (Original post by the_googly)
ill be prepared for the next one then!

couldn't get my head around 9bii also

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18. Right, I don't know if I'm just being stupid here....
But the two ways I do this question I get different solutions? Does anyone know what I'm doing wrong?
19. (Original post by mamacita)

Right, I don't know if I'm just being stupid here....
But the two ways I do this question I get different solutions? Does anyone know what I'm doing wrong?
Why is the first way you did it squared?

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20. (Original post by Jimmy20002012)
Why is the first way you did it squared?

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I squared both sides so I could try and rearrange so I only have cos

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