>>588
>a=√２−１のとき,a+1/a=[?],aの２乗+1/aの２乗=[?]

a+a/1=(√2-1) + 1/(√2-1) = √2-1 + √2+1 = 2√2

a^2+(1/a)^2 =(√2-1)^2 + ( 1/(√2-1) )^2 =3-2√2 + (3+2√2) =6