1. Let vector $O A$ rotate counterclockwise around point $O$ by $\frac{\pi}{2}$ to get vector $O B$, and $2 O A+O B=(7,9)$. Then vector $O B$ $=$ . $\qquad$
1. $\left(-\frac{i 1}{5}, \frac{23}{5}\right)$.
Let $\boldsymbol{O A}=(m, n)$, then $\boldsymbol{O B}=(-n, m)$. Therefore,
$2 O A+O B=(2 m-n, 2 n+m)=(7,9)$,

i.e., $\left\{\begin{array}{l}2 m-n=7, \\ m+2 n=9 .\end{array}\right.$
Solving, we get $m=\frac{23}{5}, n=\frac{11}{5}$.
Thus, $O A=\left(\frac{23}{5}, \frac{11}{5}\right), O B=\left(-\frac{11}{5}, \frac{23}{5}\right)$.