Math Is Fun Forum

fusilli_jerry89

Member

Registered: 2006-06-23

Posts: 86

Limits (Again, sry)

For some reason I can't use the infinite/square root signs...

1) lim x->1 [x³-(sqrt(x))]/[1-(sqrt(x))]
2) lim x->-infinite (2x-1)/(sqrt(3x²+x+1))

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Limits (Again, sry)

√ ∞
I cut an pasted them from the title area.
Also you can use LaTeX in [m a t h] math here [/m a t h] tags.

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igloo myrtilles fourmis

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Limits (Again, sry)

1
Use L’Hôpital’s rule. The answer is −3.

2
We can write

. Note the minus sign outside the square root! This is because as x tends to minus infinity, 2x−1 is going to be negative.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Limits (Again, sry)

I used L'Hopital and got -5 for the first one.

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Why did the vector cross the road?
It wanted to be normal.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Limits (Again, sry)

So it is. That’s x cubed there, not x squared which I initially wrongly saw it as.

Last edited by JaneFairfax (2007-09-16 23:20:17)