Номер 148 пожалуйста

                 1           2          3               4               5             6

                 х1        х2         х3            х4              х5             х6

                 9          15         21            27              33            39

хn=(2n+1)*3      n=1    x1=(2*1+1)*3=3*3=9
                          n=2    x2=(2*2+1)*3=5*3=15
                          n=3     x3=(2*3 +1)*3=7*3=21
                          n=4     x4=(2*4 +1)*3=9*3=27
                         n=5       x5=(2*5+1)*3=11*3=33
                         n=6       x6=(2*6 +1)*3=13*3=39