# The Official Homework Help Thread!

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### #641 Baekick

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Posted 17 October 2016 - 10:16 PM

a. (P/2) - w = l

- First you need to get the "l+w" alone. That side is divisible by 2 so you divide both sides of the equation by 2. The result is P/2 = l + w. Now you need to get the l by itself, so you just subtract w on both sides. There's your answer.

b. (2A/h) = b

- First you need to get rid of the 2 on the right side. To do this you multiply both sides of the equation by 2. The result is 2A = bh. Now all you have to do is divide both sides by h to get b by itself.

Is this what you're looking for?

Yes! Thank you so much!    I really appreciate your help.

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Posted 18 October 2016 - 12:43 AM

i desperatly need help finding a secondary source on the pearl harbor attack

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### #643 Guardian of the Galaxy

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Posted 18 October 2016 - 01:47 AM

All good, their way just seems messy to me anyway :P

If you don't mind, could you explain why they didn't use product rule for the (1+x)ln(1+x)? The final answer they got is what we're meant to get, but I don't really understand why the product rule wasn't used.

http://i.imgur.com/NP9egYR.png...

It is product rule; the first term (1 + x) * 1/(1+x) is (1+x) times the derivative of ln(1+x), and the second term ln(1+x) * 1 is ln(1+x) times the derivative of (1+x). Then minus one for the last term.

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Posted 21 October 2016 - 06:51 PM

can someone tell me how this sounds so far?

Spoiler

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### #645 steph33

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Posted 16 November 2016 - 11:43 AM (Edited by steph33, 16 November 2016 - 11:46 AM.)

hey..need help with this geometry task (imgur.com/eYcpHTU)..tried everything I could think of (calculating a radius of sphere as a circle inside an equilateral triangle; creating a new triangle with sphere's radius as one of catheti and then using cos, sin, tan formulas) but nothing so far..hope you have some ideas..I'm not asking for the solution but just some hints..don't want to to site like enotes.com/homework-help or yourhomeworkhelp.org ...

PS sorry that my very first post is about asking for help but I do need it..thanks

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### #646 dorkyu

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Posted 16 November 2016 - 11:39 PM (Edited by dorkyu, 16 November 2016 - 11:45 PM.)

Just here to say that I can help with math (through multivariable calculus and linear algebra) and computer science (my most confident subjects tbh, I can also do any science other than bio) so PM me if you need any help!

hey..need help with this geometry task (imgur.com/eYcpHTU)..tried everything I could think of (calculating a radius of sphere as a circle inside an equilateral triangle; creating a new triangle with sphere's radius as one of catheti and then using cos, sin, tan formulas) but nothing so far..hope you have some ideas..I'm not asking for the solution but just some hints..don't want to to site like enotes.com/homework-help or yourhomeworkhelp.org ...

PS sorry that my very first post is about asking for help but I do need it..thanks

This looks like an AMC problem...

I'm not entirely sure either if it's restricted to non-calculus, but I have some clue if Mathematica/multivariable calc was allowed; another thing that might help (I think you probably already know this) is the distance from the center of the sphere to the top (where it's level with the tip of the cones) is the same as the distance from the center to the 3 tangent points.

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### #647 jooyoungsbae

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Posted 16 November 2016 - 11:42 PM

Need help on stats, what exactly is a cluster sample and when would you use it? i get confused

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### #648 Aquashakencola

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Posted 20 November 2016 - 04:40 PM

hey is anyone good at chemistry here?

calculate the molar mass of acetylsalicylic acid (Asprin), C9H804(S)

ive been workin on this question for a long ass time and im still stuck help

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### #649 Athena

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Posted 20 November 2016 - 04:44 PM (Edited by Athena, 20 November 2016 - 04:46 PM.)

hey is anyone good at chemistry here?

ive been workin on this question for a long ass time and im still stuck help

So you multiply the mass of each element times the subscript next to it and then add them all up:

Carbon = 9 x 12.011 = 108.099
Hydrogen = 8 x 1.0080 = 8.0640
Oxygen = 4 x 16 = 64

Molar Mass = 108.099 + 8.0640 + 64 =
180.2 g/mol
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### #650 Aquashakencola

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Posted 20 November 2016 - 04:57 PM

So you multiply the mass of each element times the subscript next to it and then add them all up:

Carbon = 9 x 12.011 = 108.099
Hydrogen = 8 x 1.0080 = 8.0640
Oxygen = 4 x 16 = 64

Molar Mass = 108.099 + 8.0640 + 64 =
180.2 g/mol

oops i though you had to multiply them all together

thanks bby~

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### #651 Jessicaberry

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Posted 26 November 2016 - 08:46 PM (Edited by Jessicaberry, 26 November 2016 - 09:27 PM.)

Is anyone here a native speaker of Spanish and can I interview you for like 5 min I'll give you won

Nvm but in case I need a backup you can PM me or add me on Skype berryjessica_

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### #652 Meruem

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Posted 19 December 2016 - 09:58 AM (Edited by Meruem, 19 December 2016 - 09:58 AM.)

need help with first question, don't know how to set up the equation

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### #653 Guardian of the Galaxy

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Posted 19 December 2016 - 12:26 PM

need help with first question, don't know how to set up the equation

http://i.imgur.com/4cPP19G.jpg...

Let v be the speed in km/hr they traveled on the first day, and t be how long it took on the first day.

"On the first day they covered 960 km"

v*t = 960

Based on the other information you know the average speed on the second day was 10 km/hr slower (i.e., v - 10) and the trip in total took 20 hr, so they spent 20 - t hours on the second day. The distance they had to travel was 1520 - 960 = 560 km, so your equation is:

(v - 10)(20 - t) = 560

So substituting t = 960/v in the second equation:

(v - 10)(20 - 960/v) = 560

20v - 960 - 200 + 9600/v = 560

20v + 9600/v = 1720

20v^2 - 1720*v + 9600 = 0

Which has solutions v = 80 and v = 6, but it can't be 6 as they went 10 km/hr slower than that, so the speed on day 1 was 80 km/hr and on day 2, 70 km/hr.

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### #654 jooyoungsbae

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Posted 10 January 2017 - 11:55 PM

in spanish class i have a presentation on this question:

Que desafios presentan los cambios en la estructura familiar para las comunidades?

which translates to (i think) "What challenges do changes in family structure have for communities?"

i dont even know how to answer this in english ://

can someone help me out ):

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### #655 elfxo1997

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Posted 18 January 2017 - 04:14 AM

I'm not sure if this question belongs here or not but...

I have to write a semester report for Intro to Clinical Psychology, and I chose the topic "Assessment, characteristic features and treatment of Anxiety Disorders".  The word limit is around 2000 words. I'm not sure what exactly "characteristic features" include. Is it like the cause and prevalence and so on? and assessment is the diagnostic? Is it ok if I write about different disorders like phobias, social anxiety disorders,... for each paragraph?

Sorry if I ask too much. It's my first psychology paper and I have no idea where to begin

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### #656 Spring By Chance

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Posted 19 January 2017 - 01:51 PM

I'm not sure if this question belongs here or not but...

I have to write a semester report for Intro to Clinical Psychology, and I chose the topic "Assessment, characteristic features and treatment of Anxiety Disorders".  The word limit is around 2000 words. I'm not sure what exactly "characteristic features" include. Is it like the cause and prevalence and so on? and assessment is the diagnostic? Is it ok if I write about different disorders like phobias, social anxiety disorders,... for each paragraph?

Sorry if I ask too much. It's my first psychology paper and I have no idea where to begin

characteristic features are the signs and symptoms that would help doctors make their diagnosis. For example, characteristic features of social anxiety disorder include dizziness, nausea, and a rapid heartbeat in social settings, avoidance of social situations, fear of humiliation, fear that if they say something wrong the other person would hate them forever, muscle tension, the list goes on. Yes, assessment would be the diagnostic.

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Posted 19 January 2017 - 02:37 PM

can someone help me out ):

I hope this isn't too late, here are some of my thoughts about that question in English (I hope you'll manage to translate them to Spanish, [I'm not a native speaker, only level B1; hmu if you really need to, I'll try]):

• if the amount of people living in extended families decreases, the responsibility of caring for the elderly, handicapped, small children is shifted - instead of family members doing unpaid work now the community has to care for them and build kindergartens, homes for the elderly and workers have to be paid -> more (underpaid) jobs, more isolated people
• many people move to cities to start nuclear families - the older generation is left behind in rural areas and there the communities start to decrease, fail to attract new members and eventually die out
• if a community is homophobic then same-sex marriage, relationships and families are a challenge for that community. (I mean a challenge that they definitely need to overcome)
• another challenge would be to be more open-minded in general towards divorces, patchwork families and foster families
• can't think of more at the moment

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### #658 elfxo1997

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Posted 21 January 2017 - 06:38 AM (Edited by elfxo1997, 21 January 2017 - 06:47 AM.)

Could anyone help me check my Clinical Psychology term paper? The topic is about hikikomori (Japan's social withdrawal). It is my first time writing a psychology paper so it probably sucks xD I will PM you the Google Docs link. Here are the evaluation criteria if you need:

Assessment Criteria are:

1.  Answer is focused on the question/issue/problem (10%)

Show how the content of the essay is relevant to the question/issue/problem.

2.  Use of external evidence (20%)

Use of externally sourced material; interpretation of this material to support argument; references properly quoted and referencing follows standard convention (APA standards)

3.  Development of argument (30 %)

Consistent and convincing reasons for point of view; reasoning matches standard form or logical structure.

4.  Critical evaluation/analysis (30%)

Evaluation of strengths and weaknesses with reasoned explanations to support evaluation.

5.  Form/Structure (5 %)

Layout has logical structure, standard essay format should be used if applicable.

6.  Command of language (5%)

Spelling, grammar, etc.

OVERALL MARK:  100%

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### #659 chanychanchan

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Posted 24 January 2017 - 11:19 PM

hi can someone help me with an integration by parts problem?

when samples of iron ore is tested for potential mining sites, the probability (0 to 1) of finding a sample that has x percentage or iron in the sample is described by 19/9(x/sqrt(1+6x)), where x is also between 0 and 1. Find the probability that a tested sample of iron ore is at least 55% iron.

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### #660 Guardian of the Galaxy

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Posted 25 January 2017 - 04:48 PM (Edited by Guardian of the Galaxy, 25 January 2017 - 04:51 PM.)

hi can someone help me with an integration by parts problem?

when samples of iron ore is tested for potential mining sites, the probability (0 to 1) of finding a sample that has x percentage or iron in the sample is described by 19/9(x/sqrt(1+6x)), where x is also between 0 and 1. Find the probability that a tested sample of iron ore is at least 55% iron.

Hi, what's the numerator and denominator in this problem? I'm assuming the x is in the numerator, the sqrt in the denominator and the whole thing is multiplied by 19/9, is this correct?

You want to calculate:

$\int_{0.55}^{1}\frac{19}{9}\cdot\frac{x}{\sqrt{1+6x}}dx$

Factor out the 19/9.

Let:

u = x

dv = (1+6x)^-1/2 dx

du = dx

v = 1/3 * (1+6x)^1/2

(Just take the derivative dv/dx to confirm that dv is correct, but the coefficient 1/3 is because you get 3 = 1/2 * 6 when you differentiate, 1/2 from power rule and 6 from chain rule on the inside)

Since int(udv) = uv - vdu, the above expression is now:

$\frac{19}{9}\cdot\left(\left ( x\cdot\frac{1}{3}\cdot\sqrt{1+6x} \right ]^{1}_{0.55} - \int_{0.55}^{1} \frac{1}{3}\cdot\sqrt{1+6x}dx \right )$

You should be able to solve the integral on the right now

EDIT: When integrating the entire function from 0 to 1, Wolfram alpha is telling me that the total probability is less than 1... could you confirm what function describes the probability for the iron ore?

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