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Think twice (Posted on 2016-09-12) Difficulty: 2 of 5
Solve for integer x:
x1/2+x1/4= 20

See The Solution Submitted by Ady TZIDON    
Rating: 5.0000 (1 votes)

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Algebraic solution | Comment 2 of 4 |
Let y = x^1/4.  
Then the original equation becomes y^2 + y - 20 = 0
It's a simple quadratic with solutions y = -5 or +4.
Therefore, x = y^4 = 625 or 64.

Since we're raising y to the 2nd or 4th power to find x, i.e., not taking roots with the attendant sign issues, there doesn't seem to be anything more.

  Posted by JayDeeKay on 2016-09-15 12:32:28
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