Least and greatest upper bound of a set

• Feb 16th 2009, 03:29 PM
mancillaj3
Least and greatest upper bound of a set
please help, i dont know how to post on latex, for example the attachment is on the link below but I dont know how to post on this message
• Feb 16th 2009, 03:52 PM
Reckoner
Just surround your $\displaystyle \text\LaTeX$ code with $$and$$. The board sets math mode automatically, so don't use dollar signs around everything.

For example:

Code:

$$\sum_{n=1}^\infty\frac1n=\frac{\pi^2}6$$
Produces

$\displaystyle \sum_{n=1}^\infty\frac1{n^2}=\frac{\pi^2}6$

Use \text{} to get regular non-math text. There are limits on the number of characters and the size of each $\displaystyle \text\LaTeX$ image, so you may need to break things up into several sections. For full paragraphs of text, like in your PDF, post the non-math text outside of the [tex] tags.
• Feb 16th 2009, 04:04 PM
mancillaj3
Find the least upper bound and the greatest lower bound of the following sets. For a given $\displaystyle \epsilon$>0, find a number in the set that exceeds (l.u.b.A)-$\displaystyle \epsilon$ and a number in the set that is smaller than (g.l.b. A)+ $\displaystyle \epsilon$.
(a). A=$\displaystyle \lbrace $$\displaystyle \frac{4+x}{x}$$\displaystyle \vert$x
$\displaystyle \geq$
1$\displaystyle \rbrace$
• Feb 16th 2009, 04:09 PM
Reckoner
Quote:

Originally Posted by mancillaj3
Find the least upper bound and the greatest lower bound of the following sets. For a given $\displaystyle \epsilon$>0, find a number in the set that exceeds (l.u.b.A)-$\displaystyle \epsilon$ and a number in the set that is smaller than (g.l.b. A)+ $\displaystyle \epsilon$.
(a). A=$\displaystyle \lbrace $$\displaystyle \frac{4+x}{x}$$\displaystyle \vert$x
$\displaystyle \geq$
1$\displaystyle \rbrace$

For the last line, try
Code:

\text A=\left\{\left.\frac{4+x}x\;\right\vert\;x\geq1\right\}
which gives

$\displaystyle \text A=\left\{\left.\frac{4+x}x\;\right\vert\;x\geq1\ri ght\}$
• Feb 17th 2009, 03:47 AM
mr fantastic
Quote:

Originally Posted by mancillaj3
Find the least upper bound and the greatest lower bound of the following sets. For a given $\displaystyle \epsilon$>0, find a number in the set that exceeds (l.u.b.A)-$\displaystyle \epsilon$ and a number in the set that is smaller than (g.l.b. A)+ $\displaystyle \epsilon$.
(a). A=$\displaystyle \lbrace $$\displaystyle \frac{4+x}{x}$$\displaystyle \vert$x
$\displaystyle \geq$
1$\displaystyle \rbrace$

So, for the record, the actual question that the OP wants an answer for is:

Quote:

Find the least upper bound and the greatest lower bound of the following sets. For a given $\displaystyle \epsilon$>0, find a number in the set that exceeds (l.u.b.A)-$\displaystyle \epsilon$ and a number in the set that is smaller than (g.l.b. A)+ $\displaystyle \epsilon$.

$\displaystyle \text A=\left\{\left.\frac{4+x}x\;\right\vert\;x\geq1\ri ght\}$
l.u.b. = 5, g.l.b. = 1. Do you see why?