35. 若平面内两条平行线l1:x+(a−1)y+2=0l_{1}:x+(a-1)y+2=0l1:x+(a−1)y+2=0与l2:ax+2y+1=0l_{2}:ax+2y+1=0l2:ax+2y+1=0间的距离为355\frac{3\sqrt{5}}{5}535,则实数a=(a=(a=( )))