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If ab not equal to 0, then a^(-1) + b^(-1) =
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carbazzy
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If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  Updated on: 05 Aug 2019, 23:05
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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
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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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BrentGMATPrepNow
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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  05 Aug 2019, 12:32
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You might want to recheck your post.
I think you meant to write "a" instead of "2"

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BrentGMATPrepNow
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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  05 Aug 2019, 12:38
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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)\(a+b/ab\)


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

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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  05 Aug 2019, 12:41
a^-1=1/a
==》 1/a + 1/b=a+b/ ab
Option E

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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  05 Aug 2019, 12:45
1/b + 1/a = (a + b) / ab

Answer is (E)

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carbazzy
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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  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!
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freedom128
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Re: If ab not equal to 0, then a^(-1) + b^(-1) = [#permalink] New post  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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Re: if AB is not equal to 0, then a^-1 + b^-1 = 1) a+b 2 -(a+b) [#permalink] New post  11 Oct 2019, 07:06
Hello from the GMAT Club BumpBot!

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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
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