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Mar28-12, 03:54 PM
P: 21,397
How about this?
3[√3+√5+√7]2 = 2[√3+√5+√7]2 + [√3+√5+√7]2

The original expression is now written as a sum of two terms. Can you finish the problem by showing that each of these terms is the square of something? I.e., can you identify A and B with the above being equal to A2 + B2?