若二次型((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)经正交变换化为((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)，则（ ）.A.((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)B.((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)C.((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)D.((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x)_(3)

若二次型((x)_(1),(x)_(2),(x)_(3))=2({x)_(1)}^2+4({x)_(2)}^2+a({x)_(3)}^2+2b(x)_(1)(x

已知二次型((x)_(1),(x)_(2),(x)_(3))=({x)_(1)}^2+a({x)_(2)}^2+({x)_(3)}^2+2b(x)_(1)(x)

用正交变换法化二次型 f ( x _ 1 , x _ 2 , x _ 3 ) = 2 x _ 1 ^ 2 + 3 x _ 2 ^ 2 + 3 x _ 3 ^

[题目]求一个正交变换 =(p)_(y), 把二次型f(x1,-|||-_(2),(x)_(3))=2({x)_(1)}^2+3({x)_(2)}^2+3(x)

28.求一个正交变换化下列二次型成标准形:-|||-(1) =2({x)_(1)}^2+3({x)_(2)}^2+3({x)_(3)}^2+4(x)_(2)(x

28.求一个正交变换化下列二次型成标准形:-|||-(1) =2({x)_(1)}^2+3({x)_(2)}^2+3({x)_(3)}^2+4(x)_(2)(x

求二次型 ((x)_(1),(x)_(2),(x)_(3))=4({x)_(2)}^2-3({x)_(3)}^2+4(x)_(1)(x)_(2)-4(x)_(1

例4 判断二次型-|||-((x)_(1),(x)_(2),(x)_(3))=(x)_(1)^2+2(x)_(2)^2+4(x)_(3)^2+2(x)_(1)(

用正交变换法 x = Py，将二次型 [ f(x_1, x_2, x_3)= x_1^2 + 5x_2^2 + x_3^2 + 4x_1x_3 ] 化为标准形为

29.已知二次型 =2({x)_(1)}^2+3({x)_(2)}^2+3({x)_(3)}^2+2a(x)_(2)(x)_(3)(agt 0) 经正交变换 x