Math question, farktions.

2009-03-09 21:34:19

#1

Defiance: Member; +438|7106

We're learning inductive proofs and in the course of one question, I had to make this step in a proof:

n+1 n n+1-n
------ - ------- = --------------
2n+3 2n+1 (2n+3)(2n+1)

If n=1, they both equal 1/15. I'm sure it's correct, but can anyone explain the principle behind how the num/denominators are combined so? Now that I think on it, this would have come in handy in many problems, but I can't find any website to explain it.

If no one can, I'll ask my teacher tomorrow, but it's better to ask other people first imo.

2009-03-09 21:42:23

#2

cowami: OY, BITCHTITS!; +1,106|6724|Noo Yawk, Noo Yawk

greatest common denominator

multiply the first fraction by the denominator of the other, multiply the second fraction by the denominator of the first

simplify, plug in 1, voila, 1/15

EDIT: Mathy bits
(n+1)(2n+1) n(2n+3) 2n²+3n+1 2n²+3n 1
-------------- - ----------- = ----------------------------- - ----------------------- = ----------------
(2n+3)(2n+1) (2n+3)(2n+1) (2n+3)(2n+1) (2n+3)(2n+1) (2n+3)(2n+1)

the '2n²'s cancel with each other, as do the '3n's, thus when you plug in 1, you get 1/15

Last edited by cowami (2009-03-09 21:46:42)

2009-03-09 22:01:15

#3

Defiance: Member; +438|7106

Ah. Looks like a coincidence that the first problem worked out so simply. A couple other random ones don't work out as easily using the "combine the top" thing from the OP. Thanks cowami.

2009-03-09 22:03:56

#4

cowami: OY, BITCHTITS!; +1,106|6724|Noo Yawk, Noo Yawk

good, i need math reassurance

calculus III has been rapefacing me

2009-03-09 22:08:44

#5

S.Lythberg: Mastermind; +429|6882|Chicago, IL

cowami wrote:
good, i need math reassurance

calculus III has been rapefacing me

triple integrals?

fun shit, especially with my soviet professor... Differential equations is better, just hold on

2009-03-09 22:09:24

#6

cowami: OY, BITCHTITS!; +1,106|6724|Noo Yawk, Noo Yawk

S.Lythberg wrote:
cowami wrote:
good, i need math reassurance

calculus III has been rapefacing me
triple integrals?

fun shit, especially with my soviet professor... Differential equations is better, just hold on

double/triple integrals aren't the problem

it's those goddamn matrices

EDIT: on a side note, though, thank canada for Maple 12

Last edited by cowami (2009-03-09 22:09:50)

2009-03-09 22:11:58

#7

S.Lythberg: Mastermind; +429|6882|Chicago, IL

cowami wrote:
S.Lythberg wrote:
cowami wrote:
good, i need math reassurance

calculus III has been rapefacing me
triple integrals?

fun shit, especially with my soviet professor... Differential equations is better, just hold on
double/triple integrals aren't the problem

it's those goddamn matrices

EDIT: on a side note, though, thank canada for Maple 12

fuck matrices, i blocked that shit out (and my 19/50 on the exam lol)

2009-03-09 22:12:45

#8

ATG: Banned; +5,233|6964|Global Command

Post in English, or as close as you can reasonably get. Spelling, grammar, punctuation, and capitalization count.

BF2S Forums Math question, farktions.

cowami wrote:

S.Lythberg wrote:

cowami wrote:

cowami wrote:

S.Lythberg wrote:

cowami wrote:

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