Determine which equation has exactly one real solution.-2x^2 - 7 =0, 5x^2 + 9x - 4 = 0, -9x^2 + 6x +1 =0, 4x^2 - 12x + 9 = 0

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).