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# If ab not equal to 0, then a^(-1) + b^(-1) =

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EMBA Programs Moderator
Joined: 03 Apr 2019
Posts: 34
Location: United States (CA)
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If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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Updated on: 05 Aug 2019, 23:05
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Difficulty:

5% (low)

Question Stats:

90% (00:28) correct 10% (00:50) wrong based on 62 sessions

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If ab not equal to 0, then $$a^{-1} + b^{-1}=$$

A. a + b
B. -(a + b)
C. 1/(a + b)
D. 2/(a + b)
E. (a + b)/ab

Originally posted by carbazzy on 05 Aug 2019, 12:24.
Last edited by Bunuel on 05 Aug 2019, 23:05, edited 2 times in total.
Renamed the topic and edited the question.
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Joined: 11 Sep 2015
Posts: 4879
GMAT 1: 770 Q49 V46
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 12:32
1
Top Contributor
You might want to recheck your post.
I think you meant to write "a" instead of "2"

Cheers,
Brent
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GMAT 1: 770 Q49 V46
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 12:38
2
Top Contributor
carbazzy wrote:
If ab not equal to 0, then $$a^-1 + b^-1$$ =

a)a+b
b)-(a+b)
c)$$1/a+b$$
d)$$2/a+b$$
e)$$a+b/ab$$

Key concept: $$x^{-n}=\frac{1}{x^n}$$

$$a^{-1} + b^{-1} = \frac{1}{a}+\frac{1}{b}$$

$$= \frac{b}{ab}+\frac{a}{ab}$$

$$= \frac{b+a}{ab}$$

Cheers,
Brent
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Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 12:41
a^-1=1/a
==》 1/a + 1/b=a+b/ ab
Option E

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GMAT 1: 720 Q49 V40
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Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 12:45
1/b + 1/a = (a + b) / ab

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Joined: 03 Apr 2019
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Location: United States (CA)
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Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 12:52
carbazzy wrote:
If ab not equal to 0, then $$a^-1 + b^-1$$ =

a)a+b
b)-(a+b)
c)$$1/a+b$$
d)$$2/a+b$$
e)$$a+b/ab$$

Thanks so much for all the replies. Made a ton of silly mistakes today!
Director
Joined: 30 Sep 2017
Posts: 922
GMAT 1: 720 Q49 V40
GPA: 3.8
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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05 Aug 2019, 13:02
carbazzy wrote:
carbazzy wrote:
If ab not equal to 0, then $$a^-1 + b^-1$$ =

a)a+b
b)-(a+b)
c)$$1/a+b$$
d)$$2/a+b$$
e)$$a+b/ab$$

Thanks so much for all the replies. Made a ton of silly mistakes today!

Try this carbazzy

You will definitely enhance your quantitative skill. https://gmatclub.com/forum/a-4-b-3-16-h ... 02011.html

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Posts: 15021
Re: if AB is not equal to 0, then a^-1 + b^-1 = 1) a+b 2 -(a+b)  [#permalink]

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11 Oct 2019, 07:06
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: if AB is not equal to 0, then a^-1 + b^-1 = 1) a+b 2 -(a+b)   [#permalink] 11 Oct 2019, 07:06