Simplify to surd form and you get a value of where and are positive integer and is non-square. What is the value of ?
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For this to simplify, we know that 3 + 2 2 can be rewritten in the form ( x + y ) 2 .
So 3 + 2 2 = ( x + y ) 2 for some rational numbers x , y .
Expanding the RHS, we have: 3 + 2 2 = x 2 + 2 x y + y .
Since 2 x y is the only irrational term on the RHS and \(2\sqrt{2})\ is the only irrational term on the LHS, we know they have to be equal.
We have: \(2x\sqrt{y}=2\sqrt{2}\) which leads to x = 1 and y = 2 .
So 3 + 2 2 = ( 1 + 2 ) 2 .
Let's plug this back in to the problem.
3 + 2 2
= ( 1 + 2 ) 2
= 1 + 2 .
So a = 1 , b = 2 . This means that our answer is a b = 1 2 = 1 2 = 2 .
This took me a grand total of 5 seconds. (Mathcounts countdown round practice haha)