# LIMITS approaches o+ - how come?

1. Nov 29, 2008

### noobie!

LIMITS approaches o+ - how come??

i encountered a few ques which makes me baffle whn i stdy about infinite limit.. as we know limit x --->0+ it will be positive infinity and when x-->o- it will be negative infinity; first of all m i rite?then..a que which i encountered was lim x --->-8+ (2x/ x+8) hw cum i get negative infinity instead of positive infinity???it makes me so confuse..so could any1 plz rectify my mistakes for those theorem???please?! thanks alot 1st..

2. Nov 29, 2008

### arildno

Re: LIMITS approaches o+ - how come??

Well, what sign will a fraction between two negative numbers have? A negative sign, or a positive sign?

3. Nov 29, 2008

### noobie!

Re: LIMITS approaches o+ - how come??

huh,umm i don't really get what u mean;but isit negative?

4. Nov 29, 2008

Re: LIMITS approaches o+ - how come??

Intuitively, $$\lim_{x \to -8^+} 2x/(x+8)$$ is what 2x/(x + 8) approaches as x approaches -8 from the right. If x is very slightly greater than -8, then 2x is negative (it's about -16), and x + 8 is a small positive number, so 2x/(x + 8) should be a large negative number. The graph below may help in visualizing what it looks like.

http://img380.imageshack.us/img380/7241/graphvn5.png [Broken]

Last edited by a moderator: May 3, 2017
5. Nov 30, 2008

### noobie!

Re: LIMITS approaches o+ - how come??

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thanks alot..rite nw i have no doubts..thanks for your kind help..thanks..

Last edited by a moderator: May 3, 2017
6. Nov 30, 2008

### noobie!

Re: LIMITS approaches o+ - how come??

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one more doubt is let say an example: [(1/x^1/3) - (1/(x-1)^4/3 ] ;its limit is x --->0+ and 0- so the answer will be positive infinity because of v sub x=o into the equation ,thus its infinity minus 3 that's why we got positive infinity same goes to 0- ???please rectify my mistakes if i have thm..thanks

Last edited by a moderator: May 3, 2017