Cannot use Sparsearray

Need to know how to code this. Solve using Wolfram Mathematica coding system. The first two pictures are the matrix being talked about in questions 1 and 2 For instance, set A to yhe tridtagonal matrix with entriesu0.5 on the iagonal, ,i-,-ai,i+1 (-0.25 on the super diagonal and sub diagonal and aeros elsewhere. Next, take b to have ith entry equal to 1/i. The radius if I-B.A is approximately 0.998