【答案】
分析:根據向量加法的平行四邊形法則,得

=

+

,從而得到

=

(

+

).由向量減法法則得

=(

-

),從而得到

=


=

(

-

),進而算出

=

+

=


+


,最后得到

=

=


-


.
解答:解:∵四邊形OADB是平行四邊形,
∴

=

-

=

+

,

=


=

(

-

)=

(

-

)
可得

=


=

(

-

),
由向量加法法則,得

=

+

=

+

(

-

)=


+


∵

=


,

=

=


,
∴

=

+

=


+

×


=


=

(

+

)
由向量減法法則,得

=

=

(

+

)-(


+


)=


-


綜上,可得

=


+


,

=

(

+

),

=


-

點評:本題在平行四邊形中求向量的線性表示式,著重考查了平面向量的基本定理、向量的加法和減法法則等知識,屬于基礎題.