F(x) = x^4-360x^2+400
F(x) = (x^2+20)^2 - 400x^2
F(x) = (x^2-20x+20)(x^2+20x+20) = Prime Number
Since the value of second factor is always positive and greater than 1 therefore, 1st factor has
to be equals to 1.
x^2-20x+20 = 1
x = 1, 19.
Putting back the values in the original equation we get f(x) = 41 and f(x) = 761.
So, the sum will be 41+761 = 802