Oh... sorry i made a mistake. a n is Arithmetic progression! d=1/5
So is an arithmetic progression of the form but what does "m" represent in your formula?
I dont know. My teacher gave me this, but i cant answer it!
Then you should probably ask your teacher what means.
If you are trying to solve for , it is the solution to this quadratic equation in :
You can use the quadratic formula. You get a mess, but I suppose that could be the solution for ...