K is the force constatnt of a spring . The work done in extending it f

1.	K is the force constatnt of a spring . The work done in extending it from l1to l2 is
Answer» K(l2-l1) k{(l1+l2)/2} `k(l2^2-l1^2)` `k/2(l2^2- l1^2)` ANSWER :D

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