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ghong14
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If u(u+v) different from 0 and u >0, is 1/(u+v) < 1/u + v?

by ghong14 Tue Jul 16, 2013 6:10 pm

If u(u+v) is not equal to 0 and u >0, is 1/(u+v) < 1/u + v?

1) u+v >0

2) v>0

OA: B

My questions is even if we know that V > 0 and U>0 How would we know that 1/(u+v) < 1/u + v?

I simplified the later to 1/ (u+v) < (1 + UV) /u. Which comes out to be U < (1+vu)(U+V). IS this the right approach?
jlucero
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Re: If u(u+v) different from 0 and u >0, is 1/(u+v) < 1/u + v?

by jlucero Thu Jul 18, 2013 4:43 pm

ghong14 Wrote:If u(u+v) is not equal to 0 and u >0, is 1/(u+v) < 1/u + v?

1) u+v >0

2) v>0

OA: B

My questions is even if we know that V > 0 and U>0 How would we know that 1/(u+v) < 1/u + v?

I simplified the later to 1/ (u+v) < (1 + UV) /u. Which comes out to be U < (1+vu)(U+V). IS this the right approach?


It looks like your miscalculation is here:
1/u + v = v/uv (not (1 + v)/uv) + u/uv = (v + u) / uv
Joe Lucero
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ghong14
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Re: If u(u+v) different from 0 and u >0, is 1/(u+v) < 1/u + v?

by ghong14 Mon Sep 02, 2013 3:39 pm

It looks like your miscalculation is here:
1/u + v = v/uv (not (1 + v)/uv) + u/uv = (v + u) / uv


Hi I think that is still not right

1/U+V= (1+UV)/U
RonPurewal
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Re: If u(u+v) different from 0 and u >0, is 1/(u+v) < 1/u + v?

by RonPurewal Tue Sep 03, 2013 1:06 pm

If u(u+v) is not equal to 0 and u >0, is 1/(u+v) < 1/u + v?


The issue here seems to be the interpretation of the purple thing, above.
I'm going to follow order of operations and assume it means
(1/u) + v.

Still, when you post mathematical expressions on a forum, please use extra parentheses, when appropriate, to help clarify notation.

My questions is even if we know that V > 0 and U>0 How would we know that 1/(u+v) < 1/u + v?


Ok, so I'm lazy and I don't like doing algebra. (In Ron's world, even making the common denominator here is "a lot of work".)

So here's what I did with this one:
* I looked at the right-hand expression (the purple expression) first, and thought, "ok, well, that's definitely more than 1/u." (i also realized that it was more than v, but there's no v in the numerator of the other expression.)
* Then I looked at the left-hand expression and realized that it's less than 1/u, since the denominator is more than u.

Done.