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

Original post by Baloney26

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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Reply 682

Stepidermis

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 :smile:

Reply 683

Can someone help of part 4bii, always kept getting it wrong.

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Reply 684

Got the yipps

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!

Reply 685

Hilton184

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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Reply 686

JF2013

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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Reply 687

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 :smile:

Reply 688

Original post by Jimmy20002012

Can someone help of part 4bii, always kept getting it wrong.

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Reply 689

Original post by CD223

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

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Reply 690

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 :smile:

Reply 691

the_googly

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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Reply 692

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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Reply 693

the_googly

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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Reply 694

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 :smile:

Reply 695

the_googly

Original post by CD223

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

ill be prepared for the next one then!

couldn't get my head around 9bii also

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Reply 696

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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Reply 697

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?

Reply 698