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Intern  B
Joined: 03 Apr 2019
Posts: 14
Location: United States (AZ)
GPA: 3.75
If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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Difficulty:   15% (low)

Question Stats: 92% (00:28) correct 8% (00:37) wrong based on 13 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, 13:24.
Last edited by Bunuel on 06 Aug 2019, 00:05, edited 2 times in total.
Renamed the topic and edited the question.
CEO  V
Joined: 12 Sep 2015
Posts: 3912
Location: Canada
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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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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CEO  V
Joined: 12 Sep 2015
Posts: 3912
Location: Canada
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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

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

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

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

Answer: E

Cheers,
Brent
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Manager  S
Joined: 29 Jun 2019
Posts: 154
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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a^-1=1/a
==》 1/a + 1/b=a+b/ ab
Option E

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Always waiting
Manager  G
Joined: 30 Sep 2017
Posts: 225
Concentration: Technology, Entrepreneurship
GMAT 1: 720 Q49 V40 GPA: 3.8
WE: Engineering (Real Estate)
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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1/b + 1/a = (a + b) / ab

Answer is (E)

Posted from my mobile device
Intern  B
Joined: 03 Apr 2019
Posts: 14
Location: United States (AZ)
GPA: 3.75
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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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!
Manager  G
Joined: 30 Sep 2017
Posts: 225
Concentration: Technology, Entrepreneurship
GMAT 1: 720 Q49 V40 GPA: 3.8
WE: Engineering (Real Estate)
Re: If ab not equal to 0, then a^(-1) + b^(-1) =  [#permalink]

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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

Posted from my mobile device Re: If ab not equal to 0, then a^(-1) + b^(-1) =   [#permalink] 05 Aug 2019, 14:02
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