Consider a spring that does not obey hooke's law very faithfully. One end of the spring is fixed. To keep the spring stretched or compressed an amount x x , a force along the x-axis with x-component fx=kx−bx2+cx3 f x = k x − b x 2 + c x 3 must be applied to the free end. Here k=100n/m k = 100 n / m , b=700n/m2 b = 700 n / m 2 , and c=12,000n/m3 c = 12 , 000 n / m 3. Note that x>0 x > 0 when the spring is stretched and x<0 x < 0 when it is compressed.