# Please get me started on showing that the following limit exists

by kingstrick
Tags: exists, limit, showing, started
 P: 108 1. The problem statement, all variables and given/known data Evaluate the limit or show it doesn't exist. (x→∞) lim ((x+2)/√x) where (x > 0) 2. Relevant equations 3. The attempt at a solution I know how to solve it if x → c but i don't know how to start it when it goes to infinity. I just need a hint as to how to start the problem.
Mentor
P: 21,397
 Quote by kingstrick 1. The problem statement, all variables and given/known data Evaluate the limit or show it doesn't exist. (x→∞) lim ((x+2)/√x) where (x > 0) 2. Relevant equations 3. The attempt at a solution I know how to solve it if x → c but i don't know how to start it when it goes to infinity. I just need a hint as to how to start the problem.
Divide each term in the numerator by √x, and then take the limit.
P: 108
 Quote by Mark44 Divide each term in the numerator by √x, and then take the limit.
Mark, thanks for responding,

so after evaluating, i found that the limit does not exists... am i correct?
work:
((x+2)/√x)/1 --- Does not exist since the numerator is always bigger than the denominator
x→∞, x > o

P: 392
Please get me started on showing that the following limit exists

 Quote by kingstrick Mark, thanks for responding, so after evaluating, i found that the limit does not exists... am i correct? work: ((x+2)/√x)/1 --- Does not exist since the numerator is always bigger than the denominator x→∞, x > o
That's not what Mark meant. You essentially have the exact same equation you started with. Remember that

$\displaystyle\frac{a + b}{c} = \frac{a}{c} + \frac{b}{c}$.
Mentor
P: 21,397
 Quote by kingstrick so after evaluating, i found that the limit does not exists... am i correct? work: ((x+2)/√x)/1 --- Does not exist since the numerator is always bigger than the denominator x→∞, x > o
In one sense, the limit doesn't exist, because (x + 2)/√x gets large without bound as x gets large. In that sense, the limit doesn't exist because it is not a finite number. For limits like this, though, we usually say that the limit is ∞.

Also, because x is approaching infinity, you don't need to say that x > 0.
P: 108
 Quote by Mark44 In one sense, the limit doesn't exist, because (x + 2)/√x gets large without bound as x gets large. In that sense, the limit doesn't exist because it is not a finite number. For limits like this, though, we usually say that the limit is ∞. Also, because x is approaching infinity, you don't need to say that x > 0.
So when x → ∞, a function will always either go to a finite number, ∞, or -∞...so will a function then always have a limit in this sense? Oh, nevermind, some functions can diverge, like f(x) = -1^x.
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P: 21,397
 Quote by kingstrick So when x → ∞, a function will always either go to a finite number, ∞, or -∞...so will a function then always have a limit in this sense? Oh, nevermind, some functions can diverge, like f(x) = -1^x.
Right, except that ##\lim_{x \to \infty}-1^x = -1##

The one you're thinking of is f(x) = (-1)x. Without parentheses, what you wrote is the same as -(1x).
 P: 108 Thank you. I think i understand now.

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