Explanation:
the degree of a polynomial determines 1:1 the number of solutions.
a quadratic equation (degree 2) has 2 solutions.
the general solution is
x = (-b ± sqrt(b² - 4ac))/(2a)
in our case
a = -4
b = -4
c = -1
so,
x = (4 ± sqrt((-4)² - 4×-4×-1))/(2×-4)
when we look at the square root
16 - 16
we see that it is 0.
the square root of 0 is 0, and there is no difference between -0 and +0.
so, we get only one (real) solution : 4/-8 = -1/2
but : formally, there are still 2 solutions (as this is a quadratic equation). they are just identical.
so, I am not sure what your teacher wants to see in this case as answer.
my answer would be 2 real identical solutions.