由韦达定理
x1+x2=-2,x1*x2=-2006
x1^2+x2^2=(x1+x2)^2-2x1*x2=4+2*2006=4016
(x1-5)(x2-5)
=x1*x2-5x1-5x2+25
=x1*x2-5(x1+x2)+25
=-2006+5*2+25
=-1971
x1^3+x2^3
=(x1+x2)(x1^2-x1x2+x2^2)
=-2*[4016-(-2006)]
=-12044
|x1-x2|
=√(x1-x2)^2
=√[(x1+x2)^2-4x1x2]
=√(4+4*2006)
=√8028
=6√223