https://s0.wp.com/latex.php?latex=%5Cdisplaystyle++%5Csum_%7Bi%3D1%7D%5En+%7Cy+%5Ccdot+R_i%7C%5E2+%5Cleq+n+%5C%7Cy%5C%7C%5E2%2F%5Clambda%5E2.&bg=ffffff&fg=000000&s=0&c=20201002