The number of values of a for which equations  x3+ax+1=0 and x4+ax2+1=0 have a common root is

Given equations are           x3+ax+1=0 or    x4+ax2+x=0              (1) and  x4+ax2+1=0             (2)From (1) - (2), we get x = 1. Thus, x = 1 is the common roots.Hence,1+a+1=0⇒a=−2