santoshs wrote:1)2^x - 2^(x-2) = 3(2^(13)), what is x?
a.9
b.11
c.13
d.15
e.17
OA : 15
Another approach: plug in the answer choices for x.
Answer choice C: x= 13
2^13 - 2^(13-2) = 3(2^13)
2^13 - 2^11 = 3(2^13)
2^11(2^2 - 1) = 3(2^13)
2^11(3) = 3(2^13)
Plugging in x=13 made the exponent on the left 2^11.
To match 2^13 on the right side of the equation, the exponent needs to be increased by 2.
Thus, x = 13+2 = 15.
The correct answer is D.
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