6. Write a polynomial function $f$ such that the line with equation $y = 2 x + 3$ is tangent to the graph of $f$ at its point with abscissa 0 and $\int _ { 0 } { 3 } f ( x ) d x = 9$.
\section*{Ministry of Education and Merit}
\section*{A002－FINAL STATE EXAMINATION OF THE SECOND CYCLE OF EDUCATION}