Ingat rumus barisan bilangan bertingkat :

Barisan bilangan tersebut :

bold 1 comma space space 5 comma space space 12 comma space space 22 comma space space 35 space space space bold 4 space space space 7 space space space space 10 space space space 13 space space space space space space bold 3 bold space space space space 3 space space space space space 3

Sehingga diketahui U subscript 1 equals 1, x subscript 1 equals 4, y subscript 1 equals 3

Nilai a :

table attributes columnalign right center left columnspacing 0px end attributes row cell 2 a end cell equals cell y subscript 1 end cell row cell 2 a end cell equals 3 row a equals cell 3 over 2 end cell end table

Nilai b :

table attributes columnalign right center left columnspacing 0px end attributes row cell 3 a plus b end cell equals cell x subscript 1 end cell row cell 3 left parenthesis 3 over 2 right parenthesis plus b end cell equals 4 row cell 9 over 2 plus b end cell equals 4 row b equals cell 4 minus 9 over 2 end cell row b equals cell fraction numerator 8 minus 9 over denominator 2 end fraction end cell row b equals cell negative 1 half end cell end table

Nilai c :

table attributes columnalign right center left columnspacing 0px end attributes row cell a plus b plus c end cell equals cell U subscript 1 end cell row cell 3 over 2 minus 1 half plus c end cell equals 1 row cell 2 over 2 plus c end cell equals 1 row c equals cell 1 minus 1 end cell row c equals 0 end table

Maka, rumus suku ke-n pada barisan bilangan tersebut adalah U subscript n equals 3 over 2 n squared minus 1 half n.