α−β=√(α+β)2−4αβ
For equation x2+ax+b=0-------(1)
Sum=−a,Product=b
For equation x2+bx+b=0---------(2)
Sum=−b,Product=b
For equation (1) ------Difference=√a2−4b
For equation (2) ------Difference=√b2−4b
Now a2−4b=b2−4b
a2−b2=0
(a−b)(a+b)=0
a+b=0 can be one of the solutions