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October 3rd, 2016, 02:29 AM   #21
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Quote:
Originally Posted by Denis View Post
Greg, I was trying to "lengthen" this useless thread
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October 3rd, 2016, 06:07 AM   #22
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Attaboy, Big Ben
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October 3rd, 2016, 06:11 AM   #23
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@v8archie

What exactly do you mean by my route?
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October 3rd, 2016, 06:14 AM   #24
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Your solution.
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October 3rd, 2016, 08:41 AM   #25
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Ah so to clarify you were talking about the steps I suggested trying. (Which I said I understood wasn't the best solution for the OP, because I forgot for a moment what you meant by the sum of 1/x + 1/y)

As opposed to finding the approximate the range of correct answers by plugging in some values and seeing if what values are close to solution so you'll know what techniques to possibly use (if you don't know what to do at the start of a problem). This was in another thread but I thought you were referring to it, since I didn't really provide a route to the OP in dealing with problems in general as opposed to showing him a way to think about this problem and what steps he could do based on that way of seeing it. And I would think that would be an unlikely thing you'd mean as my route since I also admitted I overestimated the problem. I just want to be completely clear on what you were saying.

Last edited by skipjack; December 1st, 2016 at 04:05 PM.
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October 3rd, 2016, 09:34 AM   #26
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Page#3, post#26 a'comin up!

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Originally Posted by IamHere View Post
If x + y = 4 and xy = 5, then 1/x + 1/y = ?
xy = 5 is not required, except for wrapup.

x + y = 4
1/x + 1/y = (x + y) / (xy) = 4/5 : over and out.

Take x=7 and y = 4:
1/x + 1/y = 1/7 + 1/4 = (4 + 7) / (7 * 4) = 11/28 = (x + y) / (xy)
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November 1st, 2016, 05:44 PM   #27
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V8Archie, do you mean?

$\displaystyle \frac{1}{x} + \frac{1}{y}$=

$\displaystyle \frac{y}{xy} + \frac{x}{xy}$=

$\displaystyle \frac{x+y}{xy}$=

$\displaystyle \frac{4}{5}$
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November 4th, 2016, 02:47 AM   #28
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1/x + 1/y
Take L.C.M
=(x +y)/xy ....(1)
It is given that , x+y = 4 and xy = 5
Put these values in eqation (1)
= 4/5
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November 4th, 2016, 04:12 AM   #29
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1/x + 1/y = z

x + y = xyz

4 = 5z

z = 4/5
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November 9th, 2016, 02:51 AM   #30
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(1/x) + (1/y)
= (x+y)/(xy)
Put x+y = 4, xy = 5
= 4/5
This is the required answer.
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