A particle of mass 2 units moves along the x-axis attracted toward the origin by the force whose magnitude is numerically equal to 8x. If it is inititially at rest at x= 20, find:
a) the differential equation describing the motion.
b) the positiion of the particle at any time t.
c) the speed of the particle at any time.
d) the amplitude, period, and frequency of vibration.