How to write this equation

[YA_10963798]

I need to write this equation this way > 

however the left part can't be written like ( 1/k)

Thank you 

[Werner_E · Accepted solution]

As an EQUATION you should have no problems to write it in Prime

But if the goal is not an equation but rather an ASSIGNMENT/DEFINITION of variable k.trek, you would have to rewrite it

And if you are really lazy you can let Prime's symbolics do the job

[YA_10963798]

Thankkkkkkkkkkkkkkkkkkkkk youu