Question

(√2 + 1). (√2 - 1) racional ou irracional?

Answer 1

Racional

$( \sqrt{2} +1)( \sqrt{2} -1)\\ \\ \sqrt{2}. \sqrt{2}-1. \sqrt{2}+1. \sqrt{2}-1.1\\ \\ 2-1 = 1$

Answer 2

Racional 

(√2+1)*(√2+1)
=√2.√2-1.√2+1.√2-1.1
=2-1
=1