Difference between revisions of "2005 iTest Problems/Problem 52"

(Created page with "==Problem== If the product of <math>(\sqrt2 +\sqrt3+\sqrt5) (\sqrt2 +\sqrt3-\sqrt5) (\sqrt2 -\sqrt3+\sqrt5) (-\sqrt2 +\sqrt3+\sqrt5)</math> is <math>12\sqrt6+ 6\sqrt{x}</math>...")
 
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If the product of <math>(\sqrt2 +\sqrt3+\sqrt5) (\sqrt2 +\sqrt3-\sqrt5) (\sqrt2 -\sqrt3+\sqrt5) (-\sqrt2 +\sqrt3+\sqrt5)</math> is <math>12\sqrt6+ 6\sqrt{x}</math> , find <math>x</math>.
 
If the product of <math>(\sqrt2 +\sqrt3+\sqrt5) (\sqrt2 +\sqrt3-\sqrt5) (\sqrt2 -\sqrt3+\sqrt5) (-\sqrt2 +\sqrt3+\sqrt5)</math> is <math>12\sqrt6+ 6\sqrt{x}</math> , find <math>x</math>.
  
Note: This problem was thrown out of the actual competition.
+
IMPORTANT NOTE: This problem was thrown out of the actual competition.
 +
 
 
==Solution (credit to Mathzeus1024)==
 
==Solution (credit to Mathzeus1024)==
 
The entire product computes to <math>24</math>. Thus:
 
The entire product computes to <math>24</math>. Thus:

Latest revision as of 21:44, 19 October 2025

Problem

If the product of $(\sqrt2 +\sqrt3+\sqrt5) (\sqrt2 +\sqrt3-\sqrt5) (\sqrt2 -\sqrt3+\sqrt5) (-\sqrt2 +\sqrt3+\sqrt5)$ is $12\sqrt6+ 6\sqrt{x}$ , find $x$.

IMPORTANT NOTE: This problem was thrown out of the actual competition.

Solution (credit to Mathzeus1024)

The entire product computes to $24$. Thus:

$\sqrt{x} = \frac{24 - 12\sqrt{6}}{6} = 4 - 2\sqrt{6}$;

or $x = [4 - 2\sqrt{6}]^2 = 40 - 16\sqrt{6}$.

Note: The problem writers intended for it to equal a value where $x$ was an integer. This appears to be why it was thrown out.

See Also

2005 iTest (Problems, Answer Key)
Preceded by:
Problem 51
Followed by:
Problem 53
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