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Mathematics 24 Online
OpenStudy (anonymous):

Need help with a 2 sided limit question. Will post when i start question. Easier to use equation formatter

OpenStudy (anonymous):

Use the given graph to determine the limit, if it exists. *graph supplied* http://postimg.org/image/d9s8oel7r/ \[\lim_{x \rightarrow 2-}\] and \[\lim_{x \rightarrow 2+}\]

OpenStudy (phi):

the limit is the value you "approach" as x approaches (but *never* reaches) 2 from the left for 2- and from the right moving left to 2+

OpenStudy (anonymous):

Alright. How do i use the graph to determine it?

OpenStudy (phi):

your question left out a detail. I assume they want (for example) \[ \lim_{x\rightarrow 2^-}\ f(x)\]

OpenStudy (phi):

and f(x) is the value of the function i.e. the y value

OpenStudy (anonymous):

Ah when typing the information in i forgot to input f(x) for each lim x-> 2- or lim x-> 2+

OpenStudy (phi):

I assume you can read off f(0) from the graph ?

OpenStudy (anonymous):

I think so

OpenStudy (phi):

put your finger on 0 on the x-axis, move up until you reach the line. what y value are you at ?

OpenStudy (anonymous):

positive 5

OpenStudy (phi):

and what do you get for f(2-) (by 2- I mean just a bit to the left of 2)

OpenStudy (anonymous):

y is at 5 x would then be 1.9?

OpenStudy (phi):

in theory x is at 1.999999999.... as many 9's as you want. but you never "get" to the open circle at 2, so f(x) will be 5 f(x) is 5 until x gets to *exactly* 2, when f(2) is 1 (the black dot)

OpenStudy (phi):

the idea is the limit of f(2-) is 5 (because limits *never* allow x to be 2, just to approach it)

OpenStudy (phi):

now do f(2+) which is the value of f at just a bit to the right of 2

OpenStudy (anonymous):

2.0000000000000(you can keep going for ages)1

OpenStudy (phi):

yes, but what is f at that x?

OpenStudy (anonymous):

-2?

OpenStudy (phi):

yes that is the limit

OpenStudy (anonymous):

Alright. So its two limits i put down? 5 and -2? Thank you phi. you have been a huge help

OpenStudy (phi):

yes

OpenStudy (anonymous):

Sweet. going to close the question now. Have a good day

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