Solve z2=−9z^2 = -9z2=−9 for zzz.
z=3iz = 3iz=3i or z=−3iz = -3iz=−3i
z=3z = 3z=3 or z=−3z = -3z=−3
z=iz = iz=i or z=−iz = -iz=−i
z=9iz = 9iz=9i or z=−9iz = -9iz=−9i