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x^4 + y^4 = 100 what is the greatest value of x between?

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lpelaez
 Post subject: x^4 + y^4 = 100 what is the greatest value of x between?
 Post Posted: Sun Aug 24, 2008 11:36 pm 
Image


answer is between 3 to 6. how do i solve this for x maximum?

thanks in advance.
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TakingGMAT
 Post subject: x^4 + y^4 = 100 what is the greatest value of x between
 Post Posted: Mon Aug 25, 2008 2:19 am 
For maximum value of X, take minimum value for y. So take y=1
now x^4=100-1=99
x= 99^1/4 = 3.15 ....
so value of x lies between 3 to 6
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esledge
 Post subject:
 Post Posted: Sat Sep 27, 2008 5:37 pm 
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ManhattanGMAT Staff


Posts: 903
Location: St. Louis, MO
Actually, the minimum value for y^4 is 0, as y can be anything and y^4 cannot be negative.

But the logic is the same:
max x^4 + min y^4 = 100
max x^4 + 0 = 100
max x^2 = sqrt(100) = 10
max x = sqrt(10) = more than 3 but less than 4.

In the future, please type in the question rather than attaching a graphic unless there is a required picture. Thanks!

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Emily Sledge
Instructor
ManhattanGMAT
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