The work done by external agent in stretching a spring of force constant k from length l_1 to l_2is

The work done by external agent in stretching a spring of force consta

1.	The work done by external agent in stretching a spring of force constant k from length l_1 to l_2is
Answer» `K (l_2^2 - l_1^2)` `1/2 k(l_2^2 - l_1^2)` `k(l_2 - l_1)` `1/2k(l_2 + l_1)` ANSWER :B