K is the force constant of a spring. The work done is increasing its extension from I_(1) to I_(1) will be

K is the force constant of a spring. The work done is increasing its e

1.	K is the force constant of a spring. The work done is increasing its extension from I_(1) to I_(1) will be
Answer» `K(I_(2)-I_(1))` `K/2(l_(2)+l_(1))` `K(l_(2)^(2)-I_(1)^(2))` `K/2(l_(2)^(2)-l_(1)^(2))` ANSWER :D