At each n =1,2,3,4,... the table replaces either a(n) or b(n) by the value of x(n) that is in the previous row. The problem is, sometimes x(n) replaces a(n) in the next row, and sometimes x(n) replaces b(n) in the next row. So how would I decide whether to replace a(n) or b(n)?

for example, in row 2(n=2), b(n) is replaced by x(n)=0.26. If i where to instead replace a(n) by x(n)=0.26, would it still be correct?