# Thread: use sequences to guess which points of f has a limit

1. ## use sequences to guess which points of f has a limit

Sorry this is the last question i was confused with on my new review sheet. However I'm pretty sure I wont figure this answer out as soon as i post (sorry about that) so im sure this time i need help

Define f : R->R as follows:

f(x)= 8x if x is a rational number
f(x)= 2 $x^2$+8 if x is an irrational number.

use sequences to guess at which points f has a limit, then use $\epsilon$'s and $delta$'s to justify your conclusions.

2. Originally Posted by tn11631
Sorry this is the last question i was confused with on my new review sheet. However I'm pretty sure I wont figure this answer out as soon as i post (sorry about that) so im sure this time i need help

Define f : R->R as follows:

f(x)= 8x if x is a rational number
f(x)= 2 $x^2$+8 if x is an irrational number.

use sequences to guess at which points f has a limit, then use $\epsilon$'s and $delta$'s to justify your conclusions.
Consider sequences of rational and irrational points respectively.

3. Originally Posted by Drexel28
Consider sequences of rational and irrational points respectively.
idk what it is, but im drawing a blank on this one. Like 8x as x->1/2 , and 2x^2+8 x-> sqrt(2)?

4. Originally Posted by tn11631
idk what it is, but im drawing a blank on this one. Like 8x as x->1/2 , and 2x^2+8 x-> sqrt(2)?
I don't see where you used sequences there.

5. Originally Posted by Drexel28
I don't see where you used sequences there.
ah i'm confusing myself more..lol