If one of the roots of the equation x2+ax+b=0 and x2+bx+a=0 is coincident, then the numerical value of (a+b) is
If α is the coincident root, then α2+aα+b=0 and α2+bα+a=0 ⇒a2a2−b2=ab−a=1b−a ⇒α2=−(a+b);α=1⇒−(a+b)=1⇒(a+b)=−1