if c is -1 the equation should be
4x² + 4x -1 = 0
not plus 1
I assume you want the coordinates of the zeros.
if c is indeed -1, they are at (-1.207 , 0) and (0.207 , 0)
if c is +1, as in the equation the only zero point is at (-0.5 , 0)
see screenshot for illustration
