直线img src=zzximg/20190809/1565320469784241.png title=1565320469784241.png alt=图片33.png/的斜率为( )
①
img class=kfformula src=zzximg/20190809/1565320507335017.png data-latex=\frac {1} {2}/
②
img class=kfformula src=zzximg/20190809/1565320507148737.png data-latex=-\frac {1} {2}/
③
img class=kfformula src=zzximg/20190809/1565320507128594.png data-latex=2/
④
img class=kfformula src=zzximg/20190809/1565320507871509.png data-latex=-2/