Tentukanlah rumus suku N dan suku ke 10 dari barisan bilangan

A. barisan aritmatika 15, 25, 35, 45, 55…..
dimana a= 15
b = 25 – 15
= 10
un = a ( n – 1 ) b
= 1 ( n – 1 ) 10
= 1 + 10n – 10
= 10n + 10
n =10
un = 10n + 10
= 10 x 10 + 10
= 100 + 10
= 110
b. barisan aritmatika 24, 21, 18, 15, 12……
dimana a = 24
b = 24 – 21= 3
un = a ( n – 1 ) b
= 24 ( n – 1 ) 3
= 24 + 3n – 3
= 24 – 3 + 3n
= 21 + 3n
= 3n + 21
un = 3n + 21
un = 10
= 3 x 10 + 21
= 30 + 21
= 51
c. barisan aritmatika 20, 24, 28, 32
dimana a = 20
b = 24-20 = 4
un = a ( n – 1 ) b
= 20 ( n – 1 ) 4
= 29 + 4n – 4
= 29 – 4 + 4n
= 25 + 4n
= 4n + 25
un = 4n + 25
un = 10
= 4 x 10 + 25
= 40 + 25
= 65
semoga bermanfaat.