Question

a = (√2+3)² +(√2-1)(√2-5) aratati ca a ∈ N

Answer 1

$a=2+6\sqrt{2}+9+2-5\sqrt{2}-\sqrt{2}+5=18\in N$

Answer 2

A = (√2+3)² +(√2-1)(√2-5)
=2+6√2+9+2-5√2-√2+5
=18
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q.e.d.