It does not have any zeros, Since cos(4x)is always between -1 and +1, the first term has smallest positive velue when cos(4x) = 1 which gives, so 16 is the minimum positive value. The first term has largest negative value when cos(4x) = 1 which gives , so -8 is the maximum negative value. The graph never crosses the x-axis and thus there are no zeros at all. Edwin