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If f(x) = sqrt(2x + 5) - sqrt(x+7) / x-2 , every except x=2
and f(2)=k

and f is a continuous function at x=2, then k is equal to what?
Please show how you get the answer. THANKS a bunch!

2006-11-26 14:56:40 · 4 answers · asked by Mandali 1 in Science & Mathematics Mathematics

4 answers

For the love of all that is holy, is it really so hard to type in two pairs of parentheses? I'm really getting tired of having to guess what you people mean through esp. USE THE PROPER ORDER OF OPERATIONS, DAMNIT!



In order to make f a continuous function, it is necessary to make f(2) = [x→2]lim f(x). Therefore, we must find this quantity.

[x→2]lim (√(2x+5) - √(x+7))/(x-2)
Direct substitution yields (√9-√9)/0 → 0/0, so we use L'hopital's rule:
[x→2]lim (1/√(2x+5) - 1/(2√(x+7)))/1
Direct evaluation now yields:
1/√9 - 1/(2√9)
1/3 - 1/6
1/6

So k = [x→2]lim (√(2x+5) - √(x+7))/(x-2) = 1/6

2006-11-26 15:14:12 · answer #1 · answered by Pascal 7 · 0 0

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2016-11-27 00:29:42 · answer #2 · answered by montieth 4 · 0 0

take the limit as x goes to 2 from the left and the right

2006-11-26 15:06:45 · answer #3 · answered by elcidiv 2 · 0 0

If f(2) = k, then k is undefined.

2006-11-26 15:03:30 · answer #4 · answered by aedesign 3 · 0 1

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