A quadratic equation has exactly one real number solution.
For any quadratic equation the discriminant D is
When discriminant D> 0 then there will be 2 real solutions
When discriminant D= 0 then there will be 1 real solution
When discriminant D< 0 then there will be 2 complex solutions
Question says 'A quadratic equation has exactly one real number solution'
So Discriminant D =0