Edexcel A2 C3 Mathematics 12th June 2015

Original post by humayra.ac

I have come across questions like these a few times, how do you find a suitable starting value for an iterative formula ?

(Solomon paper A - q 8c) Thanks in advancee.

Input values of x into f(x) until you find that there is a sign change, a suitable value of Xo would be in between those two value as that is where the root lies. These are peculiar questions though because there is no obvious answer, i don't think i have every come across one on an actual edexcel paper, only on the solomon ones.

Reply 902

serandos121

what times the exam again?

Reply 903

Original post by serandos121

what times the exam again?

9:00

Reply 904

gcsestuff

ImageUploadedByStudent Room1433612403.753516.jpg

Can someone explain this to me please ?

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Reply 905

BBeyond

15

Original post by gcsestuff

Can someone explain this to me please ?

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think about the log rules, -y=-ln(3-x)/2 so -y=ln((3-x)/2)^-1 so -y=ln2/(3-x)

Reply 906

Original post by gcsestuff

Can someone explain this to me please ?

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In case you need a pic

Reply 907

JxckWilliams

GCSE stuff. First of all you multiply both sides by -1. That then gives you y = -ln((3-x)/2)
kLnX is the same thing as ln(x^k) and en something is to the power of -1 as in this case, you put it below 1, or flip the fraction. Hope this helped

Reply 908

Sathya_James

5

Original post by Gome44

I think you get need to use different letter. Why dont you choose letters, eg u and v for the product rule, and a letter like t (or anything else) for the chain. You dont always have to use u and v :smile:

Hmm, could do du/dx = du/dt times dt/dx

An example is June 2014 R question 4C

Reply 909

Could someone explain how I would simplify this please?

Reply 910

Sathya_James

5

You've linked to a file on your PC

Reply 911

gcsestuff

Thanks people I get it now !!

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Reply 912

Sathya_James

5

Weirdly that's the question I was talking about when wandering how to differentiate chain rule within a quotient rule question.

Basically you can make the top in terms of (x+1) to the minus 2/3 then divide top and bottom by it so it's 4/3 at the bottom like the question wants and that's it

Reply 913

username1194059

11

Original post by Ocean3

Could someone explain how I would simplify this please?

As all the terms are some sort of product of (X+1) you can use indicies rules to get rid of the denominator. See pic if it helps ImageUploadedByStudent Room1433613988.383107.jpg

ImageUploadedByStudent Room1433613988.383107.jpg

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Reply 914

username1194059

11

Hey guys, I was doing the January 2007 C3 paper, in which there was one question which specifically told you to draw a graph of X^4-4X-8. Naturally I didn't get the shape right and was wondering whether something like this could come up again; and if so, if there are any tricks to drawing it. Any help would be amazing!!

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Reply 915

Gome44

10

Original post by Sathya_James

Hmm, could do du/dx = du/dt times dt/dx

An example is June 2014 R question 4C

Yes. The letters are interchangeable (just make sure you define every one of them) :smile:

Reply 916

Gome44

10

Original post by ooftar

Hey guys, I was doing the January 2007 C3 paper, in which there was one question which specifically told you to draw a graph of X^4-4X-8. Naturally I didn't get the shape right and was wondering whether something like this could come up again; and if so, if there are any tricks to drawing it. Any help would be amazing!!

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Get a graphic calculator :P

Use standard graph sketching techniques. You know the turning point, classify it (the function is quite simple so you can easily find f''(x)). You know where the curve crosses the x axis from part c). Also, what happens as x tends to +- infinity, and what is f(0)

Edit: Btw, I don't think you need the exact curve. The markscheme gives marks based on the points I've mention above, so if you sketched any sort of parabolic curve you'd probably get all the marks

(edited 8 years ago)

Reply 917

Original post by Sathya_James

Weirdly that's the question I was talking about when wandering how to differentiate chain rule within a quotient rule question.

Basically you can make the top in terms of (x+1) to the minus 2/3 then divide top and bottom by it so it's 4/3 at the bottom like the question wants and that's it

Original post by ooftar

As all the terms are some sort of product of (X+1) you can use indicies rules to get rid of the denominator. See pic if it helps ImageUploadedByStudent Room1433613988.383107.jpg

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Perfect thanks a lot!

Reply 918

humayra.ac

Is this a correct method - If I draw a normal sinx graph, shift it down to -5 as that is where the minimum is, then sin x is either at 0 or -3/2pi. The answer is 3/2pi - why would it not be 0

State the minimum value of 4 sin x + 3 cos x and the smallest positive value of x for which this minimum value occurs.

5 sin(x+0,64) and the min value is -5 (worked out in part a)

Reply 919

humayra.ac