Edexcel C2 20th May 2015 Official Thread

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Reply 420

20Emily1998

Original post by husband material

Nah,

It would 3ln|x|

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Okay thank you :smile:

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Reply 421

mrchemistry

Original post by 20Emily1998

Is that core 3 or 4 because I'm confused by your working :s-smilie:

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Well you learn the differentiation of ln x in core 3, and apply it to integration in core 4 :tongue:

Reply 422

frozo123

Original post by 20Emily1998

I think so just wanted to double check as 3x^-1

Increase power so 3x^0 divided by 0 should be nothing, I think?

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It's a special case where the denominator differentiates to a magnitude of the numerator so 3/x x differentiates to 1
so integral of 3/x would be 3lnx + c

you don't need to know it for AS it's C4 shiz

Reply 423

alishahussain832

Can someone please explain part d for me.
JAN 2006 edexcel
4. The first term of a geometric series is 120. The sum to infinity of the series is 480.
(a) Show that the common ratio, r, is 3/4.
(b) Find, to 2 decimal places, the difference between the 5th and 6th terms.
(c) Calculate the sum of the first 7 terms.

The sum of the first n terms of the series is greater than 300.
(d) Calculate the smallest possible value of n.

Reply 424

Pato1

Is the leak rumour true

Reply 425

Mohammed212

Original post by Pato1

Is the leak rumour true

seriously? a leak i doubt it

Reply 426

Medicjug

Original post by alishahussain832

Can someone please explain part d for me.
JAN 2006 edexcel
4.The first term of a geometric series is 120. The sum to infinity of the series is 480.
(a)Show that the common ratio, r, is 3/4.
(b)Find, to 2 decimal places, the difference between the 5th and 6th terms.
(c)Calculate the sum of the first 7 terms.

The sum of the first n terms of the series is greater than 300.
(d)Calculate the smallest possible value of n.

ImageUploadedByStudent Room1431794062.564739.jpg

ImageUploadedByStudent Room1431794079.337202.jpg

Ask away if you have any questions! :smile:

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Reply 427

alishahussain832

Original post by Medicjug

Ask away if you have any questions! :smile:

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Thank you.

Reply 428

Anon_98

Can anyone help on question 3? Im not getting the correct answer for the predicted profit.

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Reply 429

ozzie2

Hey guys, what formulas should we know for the applications of differentiation in terms of like areas and surface area etc?

Reply 430

imran_

Guys I need help, can somebody link me a video or anything for the binomial expansion where the power is n
(2-3x)^n for example, It's never come up but I've got a good feeling it will this time

Reply 431

husband material

Original post by Anon_98

Can anyone help on question 3? Im not getting the correct answer for the predicted profit.

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Why not fam

ar^(n-1)

If 2013 is n=1
Then 2016 would be n=4

Now just plug it in :yes:

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Reply 432

Anon_98

Original post by husband material

Why not fam

ar^(n-1)

If 2013 is n=1
Then 2016 would be n=4

Now just plug it in :yes:

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Ahhhhh- haha, thank you!

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Reply 433

Medicjug

ImageUploadedByStudent Room1431799862.199617.jpg

Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?

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Reply 434

fire_and_ice

Is it worth doing the Solomon papers or should I stick to the actual papers?

Reply 435

fire_and_ice

Original post by Medicjug

Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?

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Because you're only measuring the distance from point 0 to 20. The river is a lot bigger than that (I assume).

Reply 436

username1162972

Original post by fire_and_ice

Is it worth doing the Solomon papers or should I stick to the actual papers?

Do solomons if you finish the actual ones

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Reply 437

gdunne42

Original post by Medicjug

Can anyone help can't seem to get my head round why integrating gives you the cross sectional area and not not the whole area of the river?

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What do you mean by the area of the whole river?
The equation given describes the shape of the river bed at a single point along its length.
When you find the area between this curve and the x axis (the surface of the river) you are by definition working out the cross sectional area of the river at that point.

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Reply 438

studentwiz

I don't think I'm getting the right expression for L, I did cross sectional area x L but when I sub it in to get area I don't get the answer in part b

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Reply 439

gdunne42

Original post by studentwiz

I don't think I'm getting the right expression for L, I did cross sectional area x L but when I sub it in to get area I don't get the answer in part b