已知strong/strong=(3,1),strong/strong=(x,-2),且strong/strongstrong/strong,则x的值为( )
①
img src=zzximg/20190823/1566540550755497.png title=1566540550755497.png alt=图片6.png width=17 height=45/
②
img src=zzximg/20190823/1566540562849143.png title=1566540562849143.png alt=图片7.png width=18 height=45/
③
img src=zzximg/20190823/1566540571684399.png title=1566540571684399.png alt=图片8.png width=26 height=45/
④
img src=zzximg/20190823/1566540579921674.png title=1566540579921674.png alt=图片9.png width=26 height=45/