W is known I'll give you a why you find the Z that minimizes the sum of those two terms it's going to give you a Z vector that is sparse has got lots of zeros okay and the region of space they have low energy other ones you know basically that energy once you minimize with respect to Z is the energy of every data point and because Z is constrained to be sparse it's going to be a small region of space that takes low energy and outside is going to be high energy okay so by adjusting the alpha coefficient here you can make the region