The distance a spring stretches from its "free length" is a function of how much tension is applied to it. The following table gives the spring length y that was produced in a particular spring by the given applied force f. The spring's free length is 4.7 in. Find a functional relation between / and x, the extension from the free length (x = y - 4.7).
Force / (pounds) Spring length y (inches)
0..............................................4.7
0.47...........................................7.5
1.15..........................................10.6
1.64..........................................12.9