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March 28, 2024, 08:04:10 pm

Author Topic: 3U Maths Question Thread  (Read 1230145 times)  Share 

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RuiAce

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Re: 3U Maths Question Thread
« Reply #2250 on: June 26, 2017, 01:08:34 pm »
+2
i got close to the answer, but i would really appreciate a solution so i know im not cheating my way there haahha thanks rui. your the man


dux99.95

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Re: 3U Maths Question Thread
« Reply #2251 on: June 27, 2017, 06:44:01 pm »
0
How long should it take to mark maths papers?

I complete the papers pretty fast but takes me long to mark the paper as I have to identify what rule was wrong and then find out the actual rule

RuiAce

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Re: 3U Maths Question Thread
« Reply #2252 on: June 27, 2017, 06:52:50 pm »
+3
How long should it take to mark maths papers?

I complete the papers pretty fast but takes me long to mark the paper as I have to identify what rule was wrong and then find out the actual rule
For starters, make sure you do some past papers under exam conditions. Force yourself to use the entire 2 hour block so that you actually take the time to see for yourself if you did something wrong, and not rely on the answers. Only throw the pen down once you really don't think there's anything else you can find.

You may want to scan your answers very quickly and recall what you did before you observe what the answers did. That way when you look at the answers you can compare it to what you wrote down, so you can find the error more quickly.

Ironically enough, what might be most time consuming to find are the silly mistakes. If you have a bunch of equations with lots of variables, try saying the variables in the answers out loud whilst you follow it in your own working. If you have a bunch of numbers, sometimes you might want to punch numbers into the calculator to make sure it all adds up right.

There's never a definitive rule as to how long you're 'supposed to take' to mark these things.

J.B

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Re: 3U Maths Question Thread
« Reply #2253 on: June 28, 2017, 07:25:01 am »
0
Hi,
I was wondering if someone would be able to help me with this question?
Thank you.


RuiAce

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Re: 3U Maths Question Thread
« Reply #2254 on: June 28, 2017, 09:58:03 am »
+1
Hi,
I was wondering if someone would be able to help me with this question?
Thank you.




Part a) should now be easy


J.B

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Re: 3U Maths Question Thread
« Reply #2255 on: June 28, 2017, 07:35:58 pm »
0
Thank you

K9810

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Re: 3U Maths Question Thread
« Reply #2256 on: June 28, 2017, 08:18:51 pm »
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Hey!
Need help with this question

RuiAce

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Re: 3U Maths Question Thread
« Reply #2257 on: June 28, 2017, 08:26:52 pm »
+3
Hey!
Need help with this question






bsdfjnlkasn

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Re: 3U Maths Question Thread
« Reply #2258 on: June 29, 2017, 07:58:38 am »
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Hey!

I was wondering if I could get some help with solving these multiple choice questions. I haven't see the halving the interval technique and would appreciate a brief explanation (also because it's probably fairly simple)

Also with the domain question, I get it now that I have the answer but I would like a more structured method to solving the inequality. I began by dealing with cos-1(x) and applied that to the whole function but I went wrong somewhere so if anyone could please provide the method that would be amazing.


Thank you :D

EDIT: I was wondering if someone could provide some more intermediate steps for the following proof, particularly between lines 3 and 4 that would be really helpful. I don't understand what's happened to the denominator :) . Also with proofs in general, it doesn't matter how we manipulate the function as long as we do the same to the top and bottom - right?

Thanks again :D
« Last Edit: June 29, 2017, 08:19:53 am by bsdfjnlkasn »

RuiAce

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Re: 3U Maths Question Thread
« Reply #2259 on: June 29, 2017, 09:36:15 am »
+2
Hey!

I was wondering if I could get some help with solving these multiple choice questions. I haven't see the halving the interval technique and would appreciate a brief explanation (also because it's probably fairly simple)

Also with the domain question, I get it now that I have the answer but I would like a more structured method to solving the inequality. I began by dealing with cos-1(x) and applied that to the whole function but I went wrong somewhere so if anyone could please provide the method that would be amazing.


Thank you :D

EDIT: I was wondering if someone could provide some more intermediate steps for the following proof, particularly between lines 3 and 4 that would be really helpful. I don't understand what's happened to the denominator :) . Also with proofs in general, it doesn't matter how we manipulate the function as long as we do the same to the top and bottom - right?

Thanks again :D

Same thing definitely has to be done to top and bottom
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« Last Edit: June 30, 2017, 06:24:58 pm by RuiAce »

legorgo18

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Re: 3U Maths Question Thread
« Reply #2260 on: June 30, 2017, 06:10:43 pm »
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2 questions

1) If the roots of the eqn x^3 + px^2 + qx + r=0 are consecutive terms of an AP, find an equation relating p,q and r. (What do i start with? roots be a-d, a and a+d???)

2) The probability that it rains is 2/3. What is the probability that it will rain on only 2 days during a whole week and that these 2 days are consecutive? (Stuck on 2 days being consecutive)

TYYYYY :)
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RuiAce

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Re: 3U Maths Question Thread
« Reply #2261 on: June 30, 2017, 06:22:53 pm »
+1
2 questions

1) If the roots of the eqn x^3 + px^2 + qx + r=0 are consecutive terms of an AP, find an equation relating p,q and r. (What do i start with? roots be a-d, a and a+d???)

2) The probability that it rains is 2/3. What is the probability that it will rain on only 2 days during a whole week and that these 2 days are consecutive? (Stuck on 2 days being consecutive)

TYYYYY :)
Short answer to 1) Yes. So I'll let you give it a go first. Personally, I would start with the sum of roots when the roots are in A.P.
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RuiAce

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Re: 3U Maths Question Thread
« Reply #2262 on: June 30, 2017, 06:28:40 pm »
+1
Hey!

I was wondering if I could get some help with solving these multiple choice questions. I haven't see the halving the interval technique and would appreciate a brief explanation (also because it's probably fairly simple)

Also with the domain question, I get it now that I have the answer but I would like a more structured method to solving the inequality. I began by dealing with cos-1(x) and applied that to the whole function but I went wrong somewhere so if anyone could please provide the method that would be amazing.


Thank you :D

EDIT: I was wondering if someone could provide some more intermediate steps for the following proof, particularly between lines 3 and 4 that would be really helpful. I don't understand what's happened to the denominator :) . Also with proofs in general, it doesn't matter how we manipulate the function as long as we do the same to the top and bottom - right?

Thanks again :D
Newton's method works on the basis of the x-intercepts, of the tangent at a given point. That's why in Newton's method we only ever input one point, because we rely on the tangent to do its job for us.

Halving the interval is different. Halving the interval just seeks to make the region that you're interested in (and hence you start with two points) smaller.
Take f(x)=x^2 - 9. We know that the root is at x=3, but suppose we didn't know that. We could estimate where the root is if we knew that the root was between say, 1.5 and 2.75. Then, we check the average of 1.5 and 2.75, which is 2.125, compute 2.125, and then we see that our interval can be shrunk to (2.125, 2.75).

The convenient thing about halving the interval is that you can never go outside the region of your initial values. So if your initial interval is (2,4), then you would use halving the interval when you know your root is between 2 and 4.

This is why the answer is x^2 - 5. x^2 - 5 = 0 has a root at sqrt(5), which is 2 point something. Everything else has a root that's outside the interval \( 2< x <4\)

legorgo18

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Re: 3U Maths Question Thread
« Reply #2263 on: June 30, 2017, 08:22:08 pm »
0
Hello! Quick q:

for v= root(6x) * e^-x^2 what is its square? i did 6x * e^-2x^2 not sure if its correct ty
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RuiAce

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Re: 3U Maths Question Thread
« Reply #2264 on: June 30, 2017, 08:23:10 pm »
+1
Hello! Quick q:

for v= root(6x) * e^-x^2 what is its square? i did 6x * e^-2x^2 not sure if its correct ty
Correct.

(This one may be more suitable for the 2U question thread in the future)