Answer
$0.16$, or (I)
Work Step by Step
The discriminant of a quadratic equation is equal to $b^2-4ac$, where a is the coefficient of the $x^2$ term, b is the coefficient of the x term and c is the constant number.
To have one real solution, the discriminant should equal 0. If it is $>0$, there are $2$ real solutions, and if it is $<0$, there are $2$ imaginary solutions.
$b^2-4ac = 0, (-0.8)^2 - 4*1*c = 0$
Solve for $c$:
$ 0.64-4c = 0, 0.64 = 4c, c = 0.16$
