设a1,a2,a 3为两两正交的单位向量组, _(1)=-dfrac (1)(3)(a)_(1)+dfrac (2)(3)(a)_(2)+dfrac (2)(3)(a)_(3) _(2)=-|||-dfrac (2)(3)(a)_(1)+dfrac (2)(3)(a)_(2)-dfrac (1)(3)(a)_(3) _(3)=-dfrac (2)(3)(a)_(1)+dfrac (1)(3)(a)_(2)-dfrac (2)(3)(a)_(3), 证明b1,b2,b3也是两两正交的-|||-单位向量组.