If ''a'' is a complex no. such that mod(a)=1.Find the values of,a so that equation az^2+z+1=0 has,One purely imaginary root.

Use z = iy and solve the quadratic equation and equate the real and imaginary part to zero. Then you will get the possible values of y and by that you will get the values of a. Amit Jain IIT Delhi AskIITian Faculty