1. The problem statement, all variables and given/known data It takes 3.23 J of work to stretch a Hooke's-law spring 12.1 cm from its unstressed length. How much extra work is required to stretch it an additional 5.76cm. Answer in Joules. 2. Relevant equations F= -kx W= FD 3. The attempt at a solution At first, I try using proportions to do this problem: 3.23/12.1 = x/5.76 I got that answer but it was wrong. So I tries finding the force using w=fd. Then I multiplied that by 5.76 and I got the same answer as doing it the proportion method. What am I doing wrong. Do I need K or do I need to use the equation W = 1/2kx^2? Thanks in advance.