Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing

This Question is Closed

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
method for finding \(b\) in \[\frac{5x^2+20x+6}{x(x+1)^2}=\frac{a}{x}+\frac{b}{x+1}+\frac{c}{(x+1)^2}\]
 2 years ago

mathslover Group TitleBest ResponseYou've already chosen the best response.0
in terms of a and c and x ?
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
@mahmit2012 method with derivatives
 2 years ago

Libniz Group TitleBest ResponseYou've already chosen the best response.0
what's wrong with ordinary method of finding partial differential?
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
@mahmit2012 had a snap method, but i don't understand it
 2 years ago

mathslover Group TitleBest ResponseYou've already chosen the best response.0
just a question: do wolfram has solution?
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
they have something ugly...
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
we get \(a=\frac{6}{1}=6\), and \(c=\frac{9}{1}=9\) but \[b=5+0\frac{6}{(1)^2}=1\] step i don't get
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
http://www.wolframalpha.com/input/?i=integrate+%285x%5E2%2B20x%2B6%29+%2F+%28x%5E3%2B2x%5E2%2Bx%29
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
oh the original question was an integral, btw.
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
something to do with a derivative but i don't see it
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
what's your method for B
 2 years ago

Libniz Group TitleBest ResponseYou've already chosen the best response.0
is there link to where it was done in snappier way?
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
looks like the method was, take \[5x^2+20x+6\] divide by \(x\) get \[5x+20+\frac{x}{6}\] take the derivative get \[5\frac{6}{x^2}\] and then evaluate at \(x=1\) why this works is going to bug me
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
but is sure is snapp!
 2 years ago

sauravshakya Group TitleBest ResponseYou've already chosen the best response.0
I think we can solve this making three equations....
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
i meant did you have your own way, satellite?
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
a slower... sane approach
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
i plugged in A and C.. expanded it all out... plugged in 1 for x and got B=3
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
ooooooooooooooh!!!! multiply both sides by \((x+1)^2\)!!!!!
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
but that's not right i guess
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
wowee zowee
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
how cool is that? i love it
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
@alienbrain yes i wrote my method before solved \(6+B=5\) but it required some visualization
 2 years ago

sauravshakya Group TitleBest ResponseYou've already chosen the best response.0
dw:1344137128472:dw
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
it is already solved, i was trying to understand @mahmit2012 approach
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
now i get it, maybe i can remember is @alienbrain do not multiply out, you will make an algebra mistake, it is a pain we know \(6+B=5\) and so \(B=1\)
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.3
dw:1344137486006:dw
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
@mahmit2012 my less sophisticated method was to visualize the coefficient of \(x^2\) as \(6+B\)
 2 years ago

sauravshakya Group TitleBest ResponseYou've already chosen the best response.0
@satellite73 are u sure your answer is correct.... because I got a=15 b=10 and c=1
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
yeah i am sure
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.3
dw:1344137568037:dw
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
yes i see thanks i didn't understand that you multiplied on both sides
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.3
dw:1344137675922:dw
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
i think i would not want to use this method if i had to take the derivative repeatedly
 2 years ago

mahmit2012 Group TitleBest ResponseYou've already chosen the best response.3
this is the shortest method to get cofficiant in partial fraction problem >
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
back, open study lagged me out
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
yeah it was getting laggy hope we have worn this topic out sufficiently we have the answer and a plethora of methods
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
so 5=6 + B are you just combining like terms there
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
good thing you can't throw a math book at me:)
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
ok lets go back back back
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
we know \(A=6\)
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
first term on the left is \(A(x+1)^2=6(x+1)^2\) and we also have a term that looks like \(Bx(x+1)\)
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
whatever all the other mess is when you multiply out, the only way to get \(x^2\) is from the first term, which will give you \(6x^2\) and from the second term which will give you \(Bx^2\)
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
on the other hand we know we have to end up with \(5x^2\) that tells you \(6+B=5\) and so \(B=1\)
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
ok, i got it... but the method seems to vary for each letter
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
i was hoping to avoid critical thinking and just be able to do it by a process :)
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
ok you can use one method if you like you can multiply this mess out and solve a 3 by 3 system, but i try to avoid that if at all possible because it is a ton of work try to look for values of \(x\) that will make everything zero obviously that will not work all the time when you have repeated factors but i find it much easier to use that method as far as i can once you have some of the constants, the others will be easier to find, even if you have a system of equations
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
if you have no repeated factors, the it always works
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
well, if they are linear
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
it is also very easy to make an algebra mistake when multiplying out and combining like terms, much few mistakes plugging in numbers and evaluating in any case if you were going to use "one method" you would have ended up with the equation \(A+B=5\) but think of how much easier if you know \(A=6\) already and we got \(A=6\) with almost no work
 2 years ago

satellite73 Group TitleBest ResponseYou've already chosen the best response.3
ok enough partial fractions for one night i wish @eliassaab was here to show another method it has to do with taking the limit as \(x\to \infty\) which for a rational function you can pretty much eyeball, and then determining what a constant is from that
 2 years ago

alienbrain Group TitleBest ResponseYou've already chosen the best response.0
eh.. integral of 6/x ?
 2 years ago

mathslover Group TitleBest ResponseYou've already chosen the best response.0
@vishweshshrimali5
 2 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.