f(x)=0.025x^2-0.71x+20.44
we are to solve the quadratic equation 0.025x^2-0.71x+20.44 = 0.
But in this equation, the discriminant is negative, therefore there are no real solutions.
Discriminant
b^2 - 4ac = (-0.71)^2 - 4*0.025*20.44 <--- obviously less than zero.
Complex solutions
Let us complete the square, Simplify things by multiplying everything by 40.
x^2 - 28.4 + 817.6= 0
Now complete the square.
x^2 - 28.4x + 14.2^2 - 14.2^2 + 817.6 = 0
(x - 14.2)^2 = 201.64 - 817.6
(x - 14.2)^2 = -615.96
x = 14.2 +/- i*24.81854
The complex solutions: x = 14.2 - i*24.81854, x = 14.2 + i*24.81854