√2=a-1
(a-1)^2=2
a^2-2a+1=2
a^2-2a=1
a^2-2a+1=2
a^2+1=2a+2
a^3-a^2-a+1
=a^3-2a^2+a^2-a+1
=a(a^2-2a)+a^2-a+1
=a*1+a^2-a+1
=a^2+1
=2a+2
=2(√2+1)+2
=2√2+4