# triangular inequality

• Mar 30th 2010, 02:04 PM
walleye
triangular inequality
sorry if this is the wrong section...

im just hoping that someone can verify what i have done here:

$\mid{n^2 + 2n + 1}\mid - \mid{2n^2}\mid \geq \mid{n^2 +2n + 1 + 2n^2}\mid$
• Mar 30th 2010, 02:22 PM
skeeter
Quote:

Originally Posted by walleye
sorry if this is the wrong section...

im just hoping that someone can verify what i have done here:

$\mid{n^2 + 2n + 1}\mid - \mid{2n^2}\mid \geq \mid{n^2 +2n + 1 + 2n^2}\mid$

is your inequality true for $n = 1$ ?
• Mar 30th 2010, 03:23 PM
walleye
nope :)

sorry i rephrased the question a bit wrong because i was in a hurry

i really meant it to be one of those "i dont understand what i did wrong" type questions

essentially what i was trying to do was to use the triangular inequality in the reverse, to cram the two absolute brackets into one

is anyone able to correct what i have done? or provide an alternative?
• Mar 31st 2010, 02:44 AM
HallsofIvy
Before we can tell you what you did wrong, we will have to know what you did and what you were trying to do! So far, all you have asked us to do was to verify a certain inequality which skeeter has already told you is wrong.