Question

how do the kx/l changed to kl/l??

please help me guys I know it's a silly question but I want to clarify please do answer correctly!
you cab use internet help I will be happy if you do it in a paper and then take a snap and send it to me

Answer 1

Because k mean deformation of a length

So we know that K=l (naturally l is deformation of length)

so we can do this