32. 若圆x2+y2=4x^{2}+y^{2}=4x2+y2=4与圆x2+y2+2x+ay−8=0x^{2}+y^{2}+2x+ay-8=0x2+y2+2x+ay−8=0的公共弦长为222\sqrt{2}22,则a=(a=(a=( )))