If k is the force constant of a spring the work done [against restoring force] in increasing its extension from l_(1) to l_(2) will be

If k is the force constant of a spring the work done [against restorin

1.	If k is the force constant of a spring the work done [against restoring force] in increasing its extension from l_(1) to l_(2) will be
Answer» `K(l_(2)-l_(1))` `K//2(l_(2)+l_(1))` `K(l_(2)^(2)-l_(1)^(2))` `(K)/(2)(l_(2)^(2)-l_(1)^(2))` ANSWER :4