# Thread: Need help with science/math schoolwork? Post here!

1. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by Sphere
One equation, three unknowns. What exactly are we supposed to do, call Jesus?
I don't get it.

We(or I'm) supposed to find the value of s.

2. ## Re: Need help with science/math schoolwork? Post here!

As that equation stands, it cannot be solved.

Tell us what kind of equation it is, and if u or t are some constants.

3. ## Re: Need help with science/math schoolwork? Post here!

Nah, brah. It can be solved. It's standard algebra.

4. ## Re: Need help with science/math schoolwork? Post here!

Aiight, nevermind. I found the variable.

s= (-9u-12t)/17 is the required answer.

5. ## Re: Need help with science/math schoolwork? Post here!

Well, be more clear the next time. You asked after the value of S, which is numeric.

6. ## Re: Need help with science/math schoolwork? Post here!

So right now I'm solving systems of equations using matrices and using the Gaussian Elimination or Gauss-Jordan Elimination. I have troubles knowing which row operation to use and when, especially the constant I'd use to multiply. Are there any tips to know which row operation to use, or is it a plug-and-play thing?

7. ## Re: Need help with science/math schoolwork? Post here!

So right now I'm solving systems of equations using matrices and using the Gaussian Elimination or Gauss-Jordan Elimination. I have troubles knowing which row operation to use and when, especially the constant I'd use to multiply. Are there any tips to know which row operation to use, or is it a plug-and-play thing?
Usually, teacher wants to find a triangular matrix at the end, so you'll need to do it from one end and to the other, usually from left row to right row.

but addition is associaitve, so 2x+3y+6z=8 is the same as 3y+2x+6z=8, so you should be allowed to choose the starting matrix by ordering rows differently. It's fine if you are just solving equation, but matrix are also used in geometry and changing the orders of the rows would change the referential, leading to some confusion later.

8. ## Re: Need help with science/math schoolwork? Post here!

Is it possible to determine the function fX(x) from this?

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9. ## Re: Need help with science/math schoolwork? Post here!

At first glance, it looks like integration by parts might sort things out a little. I'd try that and see if fx(x) falls out.

10. ## Re: Need help with science/math schoolwork? Post here!

I want to know how to use math and not a probability tree to find the probability of stuff before tomorrow. ( This isn't homework but my teacher said its going to be on the assessment test tomorrow and I forgot how to do it. )

You have 50 M&Ms

Half are blue, one fourth are red, 1/8 are brown, and another 1/8 are purple.

What is the probability I will pull 1 brown M&M and 2 red M&Ms first assuming I do not look. I just want to learn how to do these types of equations because I'm clueless, and Youtube isn't helping me at all.

11. ## Re: Need help with science/math schoolwork? Post here!

Well first choose a nicer number for your example. 1/8 of fifty is a fraction. Let's use 80 instead so that:

Blue = 40
Red = 20
Brown = 10
Purple = 10

Second, how you ask probability questions is very very important. If you ask what is the chance to pull 1brown, then 1 red than 1 red (order is important) it is:

(10 Browns/50 total) x (20 Reds/ 49 total) x (19 Reds/48 Total) = .032 = 3.2%

If you ask what is that chance that you pull out three and they are 1 brown and 2 reds (order is not important) that is different.

12. ## Re: Need help with science/math schoolwork? Post here!

Nevermind, just got back from school we had the assessment test already. I only came across one of those types of questions and it was about a deck of card and what are your chances of getting a red diamond card. I don't remember what I filled in but I think I got it right. ( It was mulitiple choice )

13. ## Re: Need help with science/math schoolwork? Post here!

I'm learning Factoring Special Cases and I need some help with this question:

Two square windows **( 25x^2 + 40x + 16 and x^2 - 18x + 81 )**. are shown at the right ( no picture sorry. )

How can you use the factored form of the areas to find the difference of the areas of the windows? Now
I already figured out that if you solve it without factoring you get 24x^2 + 58x -65

How do I solve it with factoring? The factored form of the first window ( starting with 25 ) is (5x + 4)^2 and the factored form of the other ( starting with x ) is (x-3)^2.

14. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by thomascreel
the other ( starting with x ) is (x-3)^2.
(x-9)^2

How do I solve it with factoring? The factored form of the first window ( starting with 25 ) is (5x + 4)^2 and the factored form of the other ( starting with x ) is (x-3)^2
a^2 - b^2 =(a+b)(a-b)

here replace by a=5x+4 and b=x-9

15. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by John Doe
(x-9)^2

a^2 - b^2 =(a+b)(a-b)

here replace by a=5x+4 and b=x-9
Thanks

+1

16. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by edse
Is it possible to determine the function fX(x) from this?

.
That looks like the result from the Laplace transform of an exponential, except that it goes down to negative infinity on the limits. I can think of a function that satisfies 0 to infinity but to do the other half is more difficult, I'd advise splitting the integral from -infinity to 0 and 0 to infinity and try to find a function that works so the sum of these two integrals adds to the final answer. Does f(x) have to be a function in the pure definition, or can it have discontinuties depending on the value of x?

17. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by Time Commander Bob
That looks like the result from the Laplace transform of an exponential, except that it goes down to negative infinity on the limits.
Kind of. It's a moment-generating function, E(etX).
I can think of a function that satisfies 0 to infinity but to do the other half is more difficult, I'd advise splitting the integral from -infinity to 0 and 0 to infinity and try to find a function that works so the sum of these two integrals adds to the final answer. Does f(x) have to be a function in the pure definition, or can it have discontinuties depending on the value of x?
I had the moment-generating function 1/(1-t) and was trying to find the probability density function f(x). I can see that I forgot to say what kind of function it was. In this case there are no negative values foe x actually. f(x)=0 for x<0.

Can you see what the function should be? I know it now.

18. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by edse
Kind of. It's a moment-generating function, E(etX). I had the moment-generating function 1/(1-t) and was trying to find the probability density function f(x). I can see that I forgot to say what kind of function it was. In this case there are no negative values foe x actually. f(x)=0 for x<0.

Can you see what the function should be? I know it now.
Ah ok, f(x) = 0 for x < 0 does make things a lot easier. I guess you got e^-x then.

19. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by Time Commander Bob
Ah ok, f(x) = 0 for x < 0 does make things a lot easier. I guess you got e^-x then.
Exactly, Exponential(1) distribution.

20. ## Re: Need help with science/math schoolwork? Post here!

Originally Posted by edse
Is it possible to determine the function fX(x) from this?

.
If you do an integration by parts as Sphere said, you'll end up with a differential equation, as t is treated as a constant here.