9. 如图,正方形ABCDABCDABCD中,MMM、NNN分别是BCBCBC、CDCDCD的中点,若AC→=λAM→+μBN→\overrightarrow{AC}=\lambda \overrightarrow{AM}+\mu \overrightarrow{BN}AC=λAM+μBN,则λ+μ=(\lambda +\mu =(λ+μ=( )))