jumlah suku pertama barisan aritmatika dinyatakan sn=3n²+4n. berapa nilai suku ke -15

U15 = S15-S15-1
=(3×15^2+4×15)-(3×14^2+4×14)
=(675+60)-(588+56)
=735-644
=91

Sn = 3n² + 4n

Jumlah 15 Suku Pertama ⬇️⬇️
Sn = 3n² + 4n
S15 = 3(15²) + 4(15)
S15 = 3 ( 225 ) + 60
S15 = 675 + 60
S15 = 735

Jumlah 14 Suku Pertama ⬇️⬇️
Sn = 3n² + 4n
S14 = 3(14²) + 4(14)
S14 = 3 ( 196 ) + 56
S14 = 588 + 56
S14 = 644

Nilai Suku ke - 15 ⬇️⬇️
U15 = S15 - S14
U15 = 735 - 644
U15 = 91 ✔️

Semoga bermanfaat.....
-Prisco