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Mathematics 15 Online
OpenStudy (surana):

Expand (n-4)^6

OpenStudy (danjs):

can you expand (n-4)^2, then you have 3 of those left (n-4)^6 = ((n-4)^2 )^3

OpenStudy (danjs):

lots of keeping track of powers of n

OpenStudy (danjs):

you should get to these as the coefficients for x^6 town to x^0 1 -24 240 -1280 3840 -6144 4096

OpenStudy (surana):

Available Answers: A: \[n^6-24n^5+240n^4-1280n^3+3480n^2-6144n+4096\] B: \[n^6+24n^5+240n^4-1280n^3+3480n^2-6144n+4096\] C: \[n^6-24n^5+240n^4-1290n^3+3840n^2-6144n+4096\] D: \[n^6-24n^5+240n^4-1280^3+3480n^2-6144n+5000\]

OpenStudy (surana):

Apologies for taking so long, it's a lot of numbers to type out.

OpenStudy (danjs):

oh.. ha you didnt have to, or take a screen shot instead maybe

OpenStudy (danjs):

if you can expand things without problem i would just use a algebra system to do it for you

OpenStudy (surana):

Expanding things is a bit of a problem for me.

OpenStudy (danjs):

it is everything from one quantity multiplied to everything from the other quantity like for this with only 2 terms in each, take 2 of the 6 (n - 4)^2 = (n-4)*(n-4) = n^2 - 4n - 4n + 16 (n-4)^2 = n^2 - 8n + 16

OpenStudy (danjs):

gets to be not fun |dw:1452146189641:dw|

OpenStudy (surana):

I see.

imqwerty (imqwerty):

u can also use the binomial expansion :)

OpenStudy (surana):

What is the binomial expansion?

OpenStudy (surana):

Also I think the answer is A.

OpenStudy (surana):

Okay.

OpenStudy (danjs):

what was the pascal triangle for again, i was thinking about that on this one

OpenStudy (danjs):

although for sure not applied

OpenStudy (surana):

I think it's for finding answers to problems like this one.

OpenStudy (danjs):

i thought they were symmetrical for the numbers

imqwerty (imqwerty):

okay so binomial expansion is like a general formula to expand \((a+b)^n\) it says that- \((a+b) ^n=~^nC_0(a)^{n-0}(b)^0+~^nC_1(a)^{n-1}(b)^1+~^nC_2(a)^{n-2}(b)^2+........+~^nC_n(a)^{n-n}(b)^n\)

OpenStudy (surana):

Sounds good.

imqwerty (imqwerty):

okay and we just gotta figure out what is our \(a\),\(b\) and \(n\) from \((n-4)^6\) and just substitute it in the equation :)

OpenStudy (surana):

I think that A would be N, B would be -4 and N would be exponent six?

imqwerty (imqwerty):

yes n will be 6 now just put those values in the equation and try to simplify it

OpenStudy (surana):

That was long. I ended up with the string of numbers associated with the first answer.

OpenStudy (danjs):

how can you know if you can take some ugly thing and go back the other way to a simple higher power single binomial?

OpenStudy (surana):

If you can get there in the first place?

imqwerty (imqwerty):

you can take binomial expansion method when you already don't know the expansion formula :) like here i didn't knew what is the formula to (a+b)6 so i used binomial expansion

OpenStudy (surana):

Okay. I'll use that.

OpenStudy (surana):

Thanks for the help, by the way.

imqwerty (imqwerty):

np :)

OpenStudy (surana):

Well, after I wrote it down, and tried it out again, I ended up with \[n^6-24n^5+240n^4-1280^3+3840n^2-6144n+4096\]

OpenStudy (danjs):

if they gave you a string of powers like that, maybe any number of em, is it possible to prove you can put that into some simpler polynomial thing

OpenStudy (danjs):

or prove you cant, either case

OpenStudy (surana):

Let me see.

OpenStudy (danjs):

like a 10^(42) term polynomial, can that be factored into some simpler form

OpenStudy (surana):

I don't think so.

OpenStudy (danjs):

well if it follows this binomial coefficients , it can but, ah nvm, just thinking

OpenStudy (surana):

I'll definitely need to work on this subject.

OpenStudy (surana):

I'll just close the problem, if it's alright with you. Thank you for all your help! :)

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