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simba12123
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exponents
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
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canuckclint
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logitech
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There has to be a typo. I assume that the questions reads like this:simba12123 wrote:If x and y are integers and
(15x + 15^(x+1))/ 4y = 15y,
what is the value of x?
2
3
4
5
Cannot be determined
cant we backsolve this bad boy? What is the best and most sure shot way?
(15^X + 15^(x+1))/ 4y = 15y
SO;
15^x+15^x15=15 4y^2
15^x(15+1)=15 4y^2
15^x = (15 y^2 ) /4
SO I belive this is where the magic is:
8)
15^x = 15 (y^2 /4)
15^x can be 1, 15, 15^2,....
Who wants to take it from here ?
LGTCH
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"DON'T LET ANYONE STEAL YOUR DREAM!"
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"DON'T LET ANYONE STEAL YOUR DREAM!"
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vishubn
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so further doing it !!Who wants to take it from here ?
Laughing
we knw x and y are integers
y^2=((15^x)*4)/15
so Left hand side should be a perfect square
a) we get y^2=60 not a perfect square
b) we get y^2=900 and y=30 , possible answer
c)we get y^2=13500 not a perfect square
d) we get y^2=202500 y=450 , possible answer !!
stuck betwwen B and D
Any more attemptS??
Vishu
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logitech
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Thanks man! - I mean MAJOR TYPO!!raunekk wrote:there is a typo here,,,
https://www.beatthegmat.com/i-don-t-unde ... 15609.html
thanks,...
LGTCH
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"DON'T LET ANYONE STEAL YOUR DREAM!"
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
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simba12123
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