- #1
Saladsamurai
- 3,020
- 7
Alrighty-then
I am really bad ay these I guess. I keep trying to reason these out, but i get stuck in the same spot every time.
Here we go...wheeeee!
Prove
[tex]\lim_{x\rightarrow1}\frac{1}{x}=1[/tex]
So I start by working 'backwards' to find a suitable [itex]\delta[/itex]
[tex]|f(x)-L|<\epsilon[/tex]
[tex]-\epsilon<\frac{1}{x}-1<\epsilon[/tex]
[tex]1-\epsilon<\frac{1}{x}<1+\epsilon[/tex]
[tex]\frac{1}{1-\epsilon}<x<\frac{1}{1+\epsilon}[/tex]
[tex]\therefore[/tex]
[tex]\frac{1}{1-\epsilon}-1<x-1<\frac{1}{1+\epsilon}-1[/tex]
Here is where I keep getting stuck. I am really bad at generalizing the inequality to find out which 'side' is closer to xo
I have assumed that [itex]0<\epsilon<1[/itex] for now.
Using that assumption and looking at each side of the inequality we have:
a) [tex]\frac{1}{1-\epsilon}-1[/tex]
AND
b) [tex]\frac{1}{1+\epsilon}-1[/tex]
But I still cannot see which of those to use. If [itex]\epsilon[/itex] is close to 0, then (a) is also close to zero and (b) is close to zero but negative.
But if [itex]\epsilon[/itex] is close to 1, then (a) becomes very large and (b) is close to 1/2.
Can someone shed some light on this?
Thanks.
I am really bad ay these I guess. I keep trying to reason these out, but i get stuck in the same spot every time.
Here we go...wheeeee!
Prove
[tex]\lim_{x\rightarrow1}\frac{1}{x}=1[/tex]
So I start by working 'backwards' to find a suitable [itex]\delta[/itex]
[tex]|f(x)-L|<\epsilon[/tex]
[tex]-\epsilon<\frac{1}{x}-1<\epsilon[/tex]
[tex]1-\epsilon<\frac{1}{x}<1+\epsilon[/tex]
[tex]\frac{1}{1-\epsilon}<x<\frac{1}{1+\epsilon}[/tex]
[tex]\therefore[/tex]
[tex]\frac{1}{1-\epsilon}-1<x-1<\frac{1}{1+\epsilon}-1[/tex]
Here is where I keep getting stuck. I am really bad at generalizing the inequality to find out which 'side' is closer to xo
I have assumed that [itex]0<\epsilon<1[/itex] for now.
Using that assumption and looking at each side of the inequality we have:
a) [tex]\frac{1}{1-\epsilon}-1[/tex]
AND
b) [tex]\frac{1}{1+\epsilon}-1[/tex]
But I still cannot see which of those to use. If [itex]\epsilon[/itex] is close to 0, then (a) is also close to zero and (b) is close to zero but negative.
But if [itex]\epsilon[/itex] is close to 1, then (a) becomes very large and (b) is close to 1/2.
Can someone shed some light on this?
Thanks.