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Onjit

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Re: Trouble for homeworks? *Post here and use pictures below*

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It's a bit wordy, but it's not too bad.

I'm mainly looking for help on constructing the matrix equation for part (b) so I can do a gaussian elimination. I've tried to do it, but I'm pretty sure my equation is wrong.

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Ratburntro44

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Re: Trouble for homeworks? *Post here and use pictures below*

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Edit: transparent background does not work well here, brb fixing
Edit 2: oops i also had a typo, brb fixing
Edit 3: ok i think everything is good now

Evilbunny

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From: The bottom of my heart

Joined: 2015-02-25

Posts: 1,276

Re: Trouble for homeworks? *Post here and use pictures below*

oh I guess someone else posted, I didn't use matrices

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Evilbunny (in cursive)

MBlood

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From: Argentina

Joined: 2016-03-01

Posts: 428

Re: Trouble for homeworks? *Post here and use pictures below*

Well when i have to study for English i came come here.

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Away.

Onjit

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Joined: 2015-02-15

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Re: Trouble for homeworks? *Post here and use pictures below*

Thanks for the help guys, it makes a lot more sense now, I was just looking at it in the wrong way. Much appreciated!

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dylantherabbit

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Joined: 2016-09-05

Posts: 93

Re: Trouble for homeworks? *Post here and use pictures below*

Okay, now I know I can't trust OP with English/LA/Grammar/Etc. homework.

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Leader of The Rabbit Squad | Managed to annoy an entire IRC for the lols. They went salty and banned me for a ridiculous time and now they want to ban me from EE itself. Learn to not be so salty peeps
The Rabbit Games Progress: 100%

Onjit

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Re: Trouble for homeworks? *Post here and use pictures below*

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Alright I have almost no idea how to do Ordinary Differential Equations, if someone could explain how to do one of the questions in part (a), I could probably figure out the rest, I'm just kind of stuck as it is.

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Nebula

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Re: Trouble for homeworks? *Post here and use pictures below*

I don't have troubles for home works.

Gosha

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From: Russia

Joined: 2015-03-15

Posts: 6,211

Re: Trouble for homeworks? *Post here and use pictures below*

I don't have troubles for home works.

Pls dont copy links font & colours

Nebula

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Re: Trouble for homeworks? *Post here and use pictures below*

I don't have troubles for home works.

Pls dont copy links font & colours

shh don't tear
just dreams
© Different55

Anatoly

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Re: Trouble for homeworks? *Post here and use pictures below*

Number 1)The notifiy's that if every student pays 75€ he will have to pay 440€ more and if every student pays 80€ then he will have 440€ left. How many students are in the school?

I don't understand the ways how to calculate and explain. You should explain the ways of calculation.

Ratburntro44

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Re: Trouble for homeworks? *Post here and use pictures below*

i don't understand the question (for some unimaginable reason it reads like a bad translation), but i'm going to go ahead and guess the answer is 88

hummerz5

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From: wait I'm not a secret mod huh

Joined: 2015-08-10

Posts: 5,853

Re: Trouble for homeworks? *Post here and use pictures below*

i don't understand the question (for some unimaginable reason it reads like a bad translation), but i'm going to go ahead and guess the answer is 88

I got 88 * 2 tho.

75p + 440 = 80p - 440
880 = 5p
176 = p

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thanks HG, HG, HG, HG! anatoly, zumza! zoey!

Ratburntro44

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Re: Trouble for homeworks? *Post here and use pictures below*

the problem is that the way the question is phrased makes barely any sense

Pingohits

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From: aids lizard

Joined: 2015-02-15

Posts: 7,591

Re: Trouble for homeworks? *Post here and use pictures below*

i attempted to decipher it (along with a tidbit to give it more sense):

1) I am the principal of the school, and I am about to buy a new device for the students. However, I need their cooperation. If every student gave me 75€, I'll have to pay an extra 440€ to meet the price. If every student gave me 80€, I'll have an extra 440€ left. How many students are in the school?

seems legible enough.

Also solution:

This question requires you to form an equation, preferably:

75s+440=80s-440

Where "s" stands for students.

The first portion [ 75s+440 ] means if an "s" amount of students paid 75€, the amount needs to be added another 440.

The second portion [80s-440 ] is similar; if "s" amount of students paid 80€, then amount needs to be subtracted 440.

Using basic algebra, subtract 75s from one side to get:

440=5s-440

Add 440 to the other:

880=5s

Divide 880 by 5 to get:

176=s

Therefore, there are 176 students in the school.

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Onjit

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Re: Trouble for homeworks? *Post here and use pictures below*

I figured I may as well dig up an old thread rather than making a new one.

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I'm generally OK with hyperbolic functions, just a bit stuck on this one.

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hummerz5

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From: wait I'm not a secret mod huh

Joined: 2015-08-10

Posts: 5,853

Re: Trouble for homeworks? *Post here and use pictures below*

so hey I'll throw out what wolfram alpha sorta spit upon me.

sinh = 1/2 (e^x - e^-x)
and we swap some variables

2x = e^y - e^-y (now they suggest making e^y = z, to simplify some...

2x = (z^2 - 1)/z

then we have a quadratic of sorts
2xz = z^2 - 1

and we solve for z I think

e^y = x + sqrt(x^2 + 1)

and then I think the logarithm thing does the last part

I pretty much just kept asking wolfram alpha what the next step should be even though I should've actually had a clue.

how'd that do?

edit: perhaps you can explain what happened to the negative part of the quadratic? I mean it should be +/- the sqrt, but we don't have that in the final solution

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thanks HG, HG, HG, HG! anatoly, zumza! zoey!

SmittyW

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Joined: 2015-03-13

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Re: Trouble for homeworks? *Post here and use pictures below*

You should know that the identity of sinhx = (e^x - e^-x)/2

To find the inverse you switch x and y and solve for y

x = sinhy
x = (e^y - e^-y)/2
2x = e^y - e^-y
2x(e^y) = (e^y - e^-y)(e^y) <--- multiply both sides by e^y. This isn't the only way to solve it
2x(e^y) = e^2y - 1
e^2y - 2x(e^y) - 1 = 0 OR (e^y)^2 - 2x(e^y) - 1 = 0

Now you use the quadratic formula to find e^y (Do it yourself aaaah)
You should get:

e^y = x +- sqrt(x^2 + 1)

You need to know that e^y > 0.
x < sqrt(x^2 + 1) so subtracting them will make e^y < 0, which isn't possible.
You can now get rid of the minus sign and take the natural log of both sides getting the solution:

y = ln(x + sqrt(x^2 + 1))

hummerz5

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From: wait I'm not a secret mod huh

Joined: 2015-08-10

Posts: 5,853

Re: Trouble for homeworks? *Post here and use pictures below*

oh wow I didn't even notice the log was au naturel

yeah, that makes sense... a positive raised anyhow is still a positive, so you can't get the -

the feels

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thanks HG, HG, HG, HG! anatoly, zumza! zoey!

Krosis

Formerly Arkonagames

Joined: 2015-06-17

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Re: Trouble for homeworks? *Post here and use pictures below*

the problem with homework for me isnt that it's hard, it's just boring, long and unnecessary

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Onjit

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Re: Trouble for homeworks? *Post here and use pictures below*

Thanks for the help guys, I really appreciate it

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Here's another one I ran into trouble with, I've tried using the definition and subbing x-->3x but that didn't turn out. (probably more to do with how i did it more than anything)

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hummerz5

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From: wait I'm not a secret mod huh

Joined: 2015-08-10

Posts: 5,853

Re: Trouble for homeworks? *Post here and use pictures below*

I want to know this as well

I thought I'd make cosh3x a thing and then try and divide out a sinh or a cosh to see if something turned up... perhaps I'm better off spelunking :b

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thanks HG, HG, HG, HG! anatoly, zumza! zoey!

Abelysk

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Re: Trouble for homeworks? *Post here and use pictures below*

Trouble for homework* just saiyan

Minisaurus

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Re: Trouble for homeworks? *Post here and use pictures below*

I don´t have any trouble for homework,
I don´t support the idea of asking here for help to do the homework, there are a lot of trolls, you know...
If you have troubles with your homework just ask your professor for help (he get paid for it, is your slave), or a good student of your classroom that don´t hate you.
If you have troubles it could be because you stay too much time in the EE forum or EE itself, i recommend to stay more time at the study room of your home and less in front of your computer playing games or commenting in social media websites and more studying...
Also eating healthy and having good habits help a lot.

Onjit

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Joined: 2015-02-15

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Re: Trouble for homeworks? *Post here and use pictures below*

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Just stuck on question (c)

I tried expanding it, but it didn't turn out

I'm going ok with the rest though.

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