The Official Homework Help Thread!

[Khyler]

Thank you!!!!!!!!!

[Jennifer]

can someone give me an example of evidence of evolution in terms of physical science?

 

idk would the environment changing be considered as evidence? i have no clue 

[Khyler]

can someone give me an example of evidence of evolution in terms of physical science?

 

idk would the environment changing be considered as evidence? i have no clue 

This video + this guy channel:

[Jennifer]

How do you do this im having a hard time doing it

And i don't know what identities (is that what you call them?) needed to do this

 

Like i know (AB)^-1AB = I and thats it im so dumb lol

Edited August 29, 2017 by metaphorical penis

[Guardian of the Galaxy]

How do you do this im having a hard time doing it

And i don't know what identities (is that what you call them?) needed to do this

 

Like i know (AB)^-1AB = I and thats it im so dumb lol

 

Left and right multiply both sides by the inverses of whatever you have on the outside until you isolate D... not sure how you could simplify further from there.

[Jennifer]

1 0 0 | 

0 3 0 |                  

0 0 2 | 

 

^would this be a upper and lower matrix or no?

me and my friends got different answers. i said it was both and they said it was neither bc it was diagonal. someone explain to me why pls

[sunnyfool]

 

1 0 0 | 

0 3 0 |                  

0 0 2 | 

 

^would this be a upper and lower matrix or no?

me and my friends got different answers. i said it was both and they said it was neither bc it was diagonal. someone explain to me why pls

 

If the entries above and below the main diagonal are all 0 then it's called a diagonal matrix So yes you are correct it is both upper and lower and also your friend is correct, it's diagonal. 

Edited August 31, 2017 by sunnyfool

[searchme]

Can someone explain to me why someone would need tutoring help in History?

 

 

Sent from my iPhone using OneHallyu

[Nobasiczone]

In the reaction represented by the equation: Fe2+ + 2e- > Fe, what is happening to Fe

-It is oxidized

-it is made disprortionate

-It is reduced

-it is neutralized

 

 

 

In a voltaic cell with electrodes made from nickel and cobalt, the cobalt is dissolved into solution as Co2+. What is the cobalt electrode called?

-cathode

-reducing electrode

-anode

-metal electrode

 

Help!

Thanks in advance for anyone who tried

<3

[Guardian of the Galaxy]

In the reaction represented by the equation: Fe2+ + 2e- > Fe, what is happening to Fe

-It is oxidized

-it is made disprortionate

-It is reduced

-it is neutralized

 

 

 

In a voltaic cell with electrodes made from nickel and cobalt, the cobalt is dissolved into solution as Co2+. What is the cobalt electrode called?

-cathode

-reducing electrode

-anode

-metal electrode

 

Help!

Thanks in advance for anyone who tried

<3

 

1) I think you mean to ask what happens to Fe²⁺; it is reduced. Just remember "LEO the lion says GER"; Losing Electrons is Oxidation, Gaining Electrons is Reduction. Since the Fe²⁺ ion gains two electrons becoming a neutral Fe atom in the process, it is reduced.

 

2) Here, you should remember "AN OX, RED CAT". That is, oxidation occurs at the anode and reduction occurs at the cathode. The cobalt electrode is having its Co atoms dissolve into Co²⁺ ions, which means that they are losing electrons, or being oxidized. So the cobalt electrode is the anode.

[Nobasiczone]

1) I think you mean to ask what happens to Fe²⁺; it is reduced. Just remember "LEO the lion says GER"; Losing Electrons is Oxidation, Gaining Electrons is Reduction. Since the Fe²⁺ ion gains two electrons becoming a neutral Fe atom in the process, it is reduced.

 

2) Here, you should remember "AN OX, RED CAT". That is, oxidation occurs at the anode and reduction occurs at the cathode. The cobalt electrode is having its Co atoms dissolve into Co²⁺ ions, which means that they are losing electrons, or being oxidized. So the cobalt electrode is the anode.

Omg thanks! I actually says Fe... so it would its neutralize?

[Guardian of the Galaxy]

Omg thanks! I actually says Fe... so it would its neutralize?

 

That's a poorly written question then, since Fe is the result of the reaction. It still sounds to me like they want you to recognize that it is a reduction reaction taking place.

[Jennifer]

do you find the determinant of elementary matrices by multiplying the diagonal altogether or is there more to it

 

im trying to look at my book and the theorem makes no sense to me

 

 

like this 

0 0 0 1 | 

0 1 0 0 |                  

0 0 1 0 | 

0 0 0 1 |

like why is dete(a) = -1

[Nobasiczone]

That's a poorly written question then, since Fe is the result of the reaction. It still sounds to me like they want you to recognize that it is a reduction reaction taking place.

thanks ! theyre correct

[Guardian of the Galaxy]

do you find the determinant of elementary matrices by multiplying the diagonal altogether or is there more to it

 

im trying to look at my book and the theorem makes no sense to me

 

 

like this 

0 0 0 1 | 

0 1 0 0 |                  

0 0 1 0 | 

0 0 0 1 |

like why is dete(a) = -1

 

Is that last row supposed to have the 1 on the left? This summarizes the determinants of elementary functions. I just looked at the proofs for these in my lin alg notes from a couple of years ago and they're really quite tedious...

[Jennifer]

Is that last row supposed to have the 1 on the left? This summarizes the determinants of elementary functions. I just looked at the proofs for these in my lin alg notes from a couple of years ago and they're really quite tedious...

Oops i wrote it wrong yeah a31 is supposed to be 1

 

So its pretty much -1 bc you have to switch the rows right?

[Guardian of the Galaxy]

Oops i wrote it wrong yeah a31 is supposed to be 1

 

So its pretty much -1 bc you have to switch the rows right?

 

Yes, it's the third type of elementary matrix listed

[Jennifer]

 

 

 

how do i do #22

[Nobasiczone]

.

Edited October 6, 2017 by ExidsJarofJamsI.M

[brumalParty]

 

 

 

how do i do #22

Do you still need help with this? You may have figured it out by now since it follows the same method with the question 23.

>>Just in case, for any vector u and v, for the two to be parallel means v can be written as u=k x v.(for k any complex number, furthermore for any k in any field F) (I have used x for the multiplication sign and in matrix ; means the row ended that is if A=[1 2; 3 4] , first row of A from left to right is 1 and 2 and the second row is 3 and 4)

>>In your question for v = (8t, -2), k must be 1/2 since (k x (-2) = -1). Since k is 1/2=> 4 = 1/2 x 8t => t = 1. Hence in (a) they are parallel for t = 1.

>>(b) v = (8t, 2t). 4 = k x 8t => k x t = 1/2 and -1 = k x 2t => k x t = -1/2. But 1/2 is not equal to -1/2 so they are never parallel.

>>© v = (1, t²) => 4 = k x 1 = k, Since k is 4, -1 = 4 x t² Hence they would be parallel for the complex numbers i/2 and -i/2 (Usually in algebra courses you would be allowed to use complex numbers but you should still check if you are allowed to use them. If you are not allowed to use them, they are never parallel, again)

 

Also for determinant, (pass this part if you are not interested in abstract linear algebra) determinant is defined as for a matrix A, (there should be permutations under Σ, since you want to sum all of the permutations up to isomorphism possible) detA=Σ(sgn(j₁....j_n)a_1j1 a_1j2 .... a_njn) where a_ijn denotes the element in the ith row and j_nth column (j_n is a permutation so it's not the same as the initial column number j) and the sgn(j₁....j_n) denotes the -1 to the power of number of permutations of elements 1,2,...,n to j₁....j_n (if you haven't taken any algebra course before, this is simply just saying the number of ways you can correctly and uniquely permute (1,2,...,n),,,, up to isomorphism of course) and defined as (-1)^{number of inversions in j1....jn} (>>further (-1)^{row num+col num} in the determinant comes from this sign of permutation)

 

Moving on/further from the abstract definition for a 2x2 matrix A=[a b; c d] , det(A) = ad-bc  (coming from definition sgn(1,2)a₁₁a₁₂ + sgn(2,1)a₁₂a₂₁) (However, I still used the definition)

 

We can use the definition to calculate the determinant of any matrix using the determinant of the 2x2 matrix which is above and would usually be given to you as a lemma (but it's a simple application of the definition),

for B=[a b c; d e f; g h i] I will use the first row to calculate the determinant however you are free to choose any row you like

det(B)=(-1)¹⁺¹a det([e f; h i]) + (-1)¹⁺²b det([d f; g i]) + (-1)¹⁺³c det([d e; g h]). (However, I still used the definition)

 

That is, you are first choosing a row then by starting from the first column, you will add the column number and the row number (this is the number of permutations) and you will calculate-1 to the power of sum you have just calculated then you will multiply it with the rest: and then you will multiply by the element which is in the intersection of the row and column you are currently in then you will disregard all the elements in the row and column you are currently in, then you will multiply by the determinant of the smaller matrix created by disregarding that row and column. Then you will move on to the next column and continue the process until the end of the row. For the new determinants you have to calculate, you have to continue this process until you get to the matrix in the form 2x2.

 

But since the abstract definition is practically useless there are some correlations and shortcuts which can help you calculate the determinants more easily, I suggest you to study them. Your teacher can probably help you. It's really easy actually, it just takes lots of works to actually use the determinant practically. If you have more questions about how to calculate them or how to prove their properties, I would love to help ^^

 

 

NOTE: Furthermore for question 22, CLAIM: for vectors u=(x₁, y₁) and v=(x₂, y₂), (assuming u and v are not the zero vector) they are said to be parallel if and only if the determinant of the matrix A = [x₁, y_1; x₂, y₂] is zero.

>>proof: if u and v are parallel then u = k x v for some k in a field. then u can be written as (kx_2, ky₂)

then det(A) = x₁y₂ - y₁x₂ = kx₂y₂ - ky₂x₂ = 0

if det(A) = 0 then x₁y₂ = y₁x₂ => x₁/x₂ = y₁/y₂ = k for some k in a field. Hence the vectors are parallel.

 

Applying the claim to your question:

(a) det([4  -1; 8t  -2]) = -8 - (-8t) = 8t - 8 Since we want u and (a) to be parallel determinant must be zero and 8t-8 is zero when t = 1.

(b)det([4  -1; 8t  2t]) = 8t - (-8t) = 16t Since we want u and (b) to be parallel determinant must be zero and 16t = 0 when t = 0 but if one of the vectors is zero then the definition fails and the vectors are not parallel.

©det([4  -1; 1 t²) = 4t² - (-1) = 4t² + 1 Since we want u and © to be parallel determinant must be zero. 4t² + 1 = 0 then 4t² = -1 then t² = -1/4 if you take the square root you will get two roots in complex numbers that are i/2 and -i/2. So the vectors are parallel for t = i/2 or t = -i/2

 

 

!!When I first posted this, I have made many mistakes but currently everything seems fine.!!

Edited October 18, 2017 by brumalParty

[Nev Schulman]

people of oh who have been to Thailand please help

https://onehallyu.com/topic/596571-adults-of-oh-that-have-been-to-thailand/

[Pananana]

Can somebody help me with organic chemistry? I need a full mechanism of catalytic hydrogenation of aromatic rings.

 

 

I'm uni student btw getting a course of medical technology major in clinical chemistry

[mynameiswonho]

I FORGOT THIS THREAD EXISTS. GUYS PLEASE HELP ME. OH MY GOD.

I have a survey I need to do for my final project, please help me by responding (if you live in the US)

It is about leisure and I will be using it to find data to help my argument on the relationship between children and institutions SAVE ME PLEASE

https://www.statcrunch.com/5.0/survey.php?surveyid=19117&code=PJUOC

[paopufruit]

Is anyone good at organic chem and can help me out??

[brumalParty]

Can somebody help me with organic chemistry? I need a full mechanism of catalytic hydrogenation of aromatic rings.

 

 

I'm uni student btw getting a course of medical technology major in clinical chemistry

 

Is anyone good at organic chem and can help me out??

I have taken advanced chemistry course in 2013 which only covered Organic Chemistry so I can try helping both of you but I am not sure how much of it I still remember.