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March 29, 2024, 10:56:06 am

Author Topic: 3U Maths Question Thread  (Read 1230446 times)  Share 

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pikachu975

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Re: 3U Maths Question Thread
« Reply #2670 on: August 18, 2017, 07:33:30 pm »
+4
hiii
what's the equation of tangent to the curve y=x^2 +2x -5 that is parallel to the line y=4x-1

dy/dx = 2x + 2
sub dy/dx = 4 because the line is parallel to y = 4x-1
2x + 2 = 4
2x = 2
x = 1

Sub x = 1 into y
y = 1 + 2 - 5
y = - 2

y + 2 = 4 (x-1)
y + 2 = 4x - 4
y = 4x - 6

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itssona

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Re: 3U Maths Question Thread
« Reply #2671 on: August 18, 2017, 07:59:57 pm »
0
dy/dx = 2x + 2
sub dy/dx = 4 because the line is parallel to y = 4x-1
2x + 2 = 4
2x = 2
x = 1

Sub x = 1 into y
y = 1 + 2 - 5
y = - 2

y + 2 = 4 (x-1)
y + 2 = 4x - 4
y = 4x - 6
ah thank you!!! :)
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Claudiaa

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Re: 3U Maths Question Thread
« Reply #2672 on: August 19, 2017, 12:11:38 pm »
0
Hi could I please get help with the following question (this is satan reincarnated aka perms topic) :) :)

A group of 5 boys and 5 girls line up outside a cinema. In how many ways can they be arranged
A) if they alternate between boys and girls ?
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Opengangs

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Re: 3U Maths Question Thread
« Reply #2673 on: August 19, 2017, 12:22:43 pm »
+4
Hi could I please get help with the following question (this is satan reincarnated aka perms topic) :) :)

A group of 5 boys and 5 girls line up outside a cinema. In how many ways can they be arranged
A) if they alternate between boys and girls ?
Hi, Claudiaa!

We can have two different arrangements:

GBGBGBGBGB
BGBGBGBGBG

We can choose to seat the girls, or the boys, first.
Seating the girls, we get 5! (G_G_G_G_G_)
Thus, the boys can only sit in 5! ways (GBGBGBGB)

This is the same number of ways as: BGBGBGBGBG

Thus, we get: 2(5!)(5!) = 28,800
« Last Edit: August 19, 2017, 12:24:41 pm by Opengangs »

Claudiaa

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Re: 3U Maths Question Thread
« Reply #2674 on: August 19, 2017, 12:31:25 pm »
0
Hi, Claudiaa!

We can have two different arrangements:

GBGBGBGBGB
BGBGBGBGBG

We can choose to seat the girls, or the boys, first.
Seating the girls, we get 5! (G_G_G_G_G_)
Thus, the boys can only sit in 5! ways (GBGBGBGB)

This is the same number of ways as: BGBGBGBGBG

Thus, we get: 2(5!)(5!) = 28,800

Thank you so much!! I went through 4 textbooks trying to find an example
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pikachu975

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Re: 3U Maths Question Thread
« Reply #2675 on: August 19, 2017, 01:16:55 pm »
+4
Hi could I please get help with the following question (this is satan reincarnated aka perms topic) :) :)

A group of 5 boys and 5 girls line up outside a cinema. In how many ways can they be arranged
A) if they alternate between boys and girls ?

Another explanation:

You can put 10 people in the first spot, then in the next spot you can put 5 (because the first spot e.g. it was a boy so next one is a girl and 5 girls left) then you can put 4, then 4 again, 3, 3, and so on so you get 10 x 4! x 5!

To think of perms and combs just think of "how many people can I put in this spot" and go from there

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itssona

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Re: 3U Maths Question Thread
« Reply #2676 on: August 19, 2017, 04:16:23 pm »
0
heey what's limit x tends to infinity for:

((-5x^3 -2x +4))/x^4
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RuiAce

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Re: 3U Maths Question Thread
« Reply #2677 on: August 19, 2017, 04:33:32 pm »
+5
heey what's limit x tends to infinity for:

((-5x^3 -2x +4))/x^4


itssona

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Re: 3U Maths Question Thread
« Reply #2678 on: August 19, 2017, 04:44:58 pm »
0

ah thank you Rui :)


last one (kinda dont know piecemeal function limits)
whats lim x-> 0
where f (x) =
x^2 +1 for x>=0
1 for x <0

Mod edit: Posts merged. At times like these, please resort to the modify function at the top right corner of a post, to refrain from double-posting.
« Last Edit: August 19, 2017, 04:55:10 pm by RuiAce »
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Re: 3U Maths Question Thread
« Reply #2679 on: August 19, 2017, 04:54:10 pm »
+5
last one (kinda dont know piecemeal function limits)
whats lim x-> 0
where f (x) =
x^2 +1 for x>=0
1 for x <0






roygbivmagic

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Re: 3U Maths Question Thread
« Reply #2680 on: August 22, 2017, 04:59:50 pm »
0
Hi! Could you please explain how to solve this?: ∫ (1 + sin2x)^0.5 dx

Opengangs

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Re: 3U Maths Question Thread
« Reply #2681 on: August 22, 2017, 05:54:19 pm »
+4
Hi! Could you please explain how to solve this?: ∫ (1 + sin2x)^0.5 dx



Wolfram will suggest this:




This suggests that both answers are valid, depending on what end we're taking. The answer Wolfram suggested is the general form to include both solutions.

RuiAce

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Re: 3U Maths Question Thread
« Reply #2682 on: August 22, 2017, 07:54:04 pm »
+3



Wolfram will suggest this:




This suggests that both answers are valid, depending on what end we're taking. The answer Wolfram suggested is the general form to include both solutions.


Edit: Typo
« Last Edit: August 22, 2017, 07:58:28 pm by RuiAce »

jamonwindeyer

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Re: 3U Maths Question Thread
« Reply #2683 on: August 23, 2017, 11:00:24 am »
0
Can I have help with q 21 and q22c please?

I'll move this to the WACE thread and answer it there :)

bsdfjnlkasn

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3U Maths Question Thread
« Reply #2684 on: August 23, 2017, 09:58:25 pm »
0
Would love some help with q5d) thank you!!


EDIT: Am also unsure of how to properly get 6b) if we weren't given part a) for guidance. In particular, the RHS coefficient, I got the right answer but am not sure what it means (I was using part a) as a model, but my understanding isn't there yet)

« Last Edit: August 23, 2017, 10:12:35 pm by bsdfjnlkasn »