If the equations x2 + px + q = 0 and x2 + p'x + q' = 0 have a common root, then it must be equal to

Equations x2 + px + q = 0 and x2 + p'x + q' = 0 have a common root. Therefore,q−q'2=pq'−p'qp'−p          (1)Subtracting two equations, we havex=q−q'p'−pAlso using (1),x=q−q'p'−p=pq'−p'qq−q'