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06 Feb 2019, 08:17
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
64% (02:21) correct
36%
(02:24)
wrong
based on 75
sessions
History
Date
Time
Result
Not Attempted Yet
GMATH practice exercise (Quant Class 14)
What is the value of \(x\) ?
\(\left( 1 \right)\,\,\,x > 0\)
\(\left( 2 \right)\,\,\,{8^x} - 12 \cdot {4^x} = 64 \cdot {2^x}\)
What is the value of \(x\) ?
\(\left( 1 \right)\,\,\,x > 0\)
\(\left( 2 \right)\,\,\,{8^x} - 12 \cdot {4^x} = 64 \cdot {2^x}\)
Mai20
Joined: 27 Mar 2018
Last visit: 17 Nov 2021
Posts: 5
Own Kudos:
Given Kudos: 2
Location: India
Concentration: Sustainability, Entrepreneurship
Schools: ISB '23 (I)
GPA: 3.7
06 Feb 2019, 23:56
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Shouldn't answer be c? option 2 is a cubic having 3 roots : -4,0,16. Thus only with point 1 can we narrow down the answer to 4.
KanishkM
Joined: 09 Mar 2018
Last visit: 18 Dec 2021
Posts: 755
Given Kudos: 123
Location: India
Schools: DeGroote'21 Desautels '21 NUS '21
07 Feb 2019, 00:14
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Mai20
Mai20
It is indeed B,
have a look here
\(2^x * 2^x * 2^x - 2^2 * 3* 2^x = 64 * 2^x\)
take \(2^x\) common from LHS and cancel it
\(2^x * 2^x - 12 * 2^x = 64\)
\(2^x\)(\(2^x\) - 12) = 64
\(2^x\) - 12 =\(2^{6-x}\)
only x = 4 will satisfy the above
\(2^4\) - 12 = \(2^2\)
4 = 4
B
