If f(x)=x10+2x9-2x8-2x7+x6+3x2+6x+1, then what is f(√(2-1))

Why f(1) = 1? 

$f(\sqrt{2-1}) = f(\sqrt{1}) = f(1)$

so $f(1)= 1^10 + 2(1)^9 - 2(1)^8 - 2(1)^7 + 1^6 + 3(1)^2 + 6(1) + 1 = 1 + 2 - 2 - 2 + 1 + 3 + 6 + 1 = 3 + 6 + 1 = 10$

so $f(1) = 10$ not 1,where im wrong?

Thanks!