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# If 5^(x^2 − 2x) = 1/5, what is the value of x ?

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Math Expert
Joined: 02 Sep 2009
Posts: 55266
If 5^(x^2 − 2x) = 1/5, what is the value of x ?  [#permalink]

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29 Nov 2018, 00:32
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Difficulty:

5% (low)

Question Stats:

86% (00:54) correct 14% (01:21) wrong based on 43 sessions

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If $$5^{x^2−2x} = \frac{1}{5}$$, what is the value of x ?

A. -1
B. 1
C. 1 + √2
D. 1 − √2
E. 1 + 2√2

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Joined: 11 Dec 2013
Posts: 120
Location: India
GMAT Date: 03-15-2015
WE: Education (Education)
Re: If 5^(x^2 − 2x) = 1/5, what is the value of x ?  [#permalink]

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29 Nov 2018, 00:44
1
5^(x^2 − 2x) = 1/5 = 5^(-1)
Hence , x^2 − 2x = -1
or x^2 − 2x + 1 = 0
(x-1)^2=0
x=1

B

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Re: If 5^(x^2 − 2x) = 1/5, what is the value of x ?  [#permalink]

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29 Nov 2018, 03:38
Bunuel wrote:
If $$5^{x^2−2x} = \frac{1}{5}$$, what is the value of x ?

A. -1
B. 1
C. 1 + √2
D. 1 − √2
E. 1 + 2√2

5^{x^2−2x} = \frac{1}{5}[/m]

x^2-2x+1=0
(x-1)(x-1)=0
x=1 IMO B
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Re: If 5^(x^2 − 2x) = 1/5, what is the value of x ?   [#permalink] 29 Nov 2018, 03:38
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