【答案】
分析:根据向量加法的平行四边形法则,得

=

+

,从而得到

=

(

+

).由向量减法法则得

=(

-

),从而得到

=


=

(

-

),进而算出

=

+

=


+


,最后得到

=

=


-


.
解答:解:∵四边形OADB是平行四边形,
∴

=

-

=

+

,

=


=

(

-

)=

(

-

)
可得

=


=

(

-

),
由向量加法法则,得

=

+

=

+

(

-

)=


+


∵

=


,

=

=


,
∴

=

+

=


+

×


=


=

(

+

)
由向量减法法则,得

=

=

(

+

)-(


+


)=


-


综上,可得

=


+


,

=

(

+

),

=


-

点评:本题在平行四边形中求向量的线性表示式,着重考查了平面向量的基本定理、向量的加法和减法法则等知识,属于基础题.