1. The problem statement, all variables and given/known data When a certain spring is stretched beyond its proportional limit, the restoring force satisfies the equation F=-kx+βx3. If k=8.7 N/m and β=95 N/m3, calculate the work done by this force when the spring is stretched 0.105 m. 2. Relevant equations W= F*d 3. The attempt at a solution I found F by plugging in the values of k, β and x=0.105 m to get -1.02. The negative for the force value makes sense here since it is a restoring force acting in the negative direction. Am i wrong in this reasoning? My answer is wrong, though since when I try W=F*d; =-1.02*.105, I get -0.107 J, which is wrong. Help!