tentukan s3 dan s4 dari masing masing deret dibawah ini a.1+2+3+4+... b.100+80+60+...

a. s3 = 3/2 (2x1 + (3-1) 1)
s3 = 3/2 (2 + 2)
s3 = 3/2 (4) = 6
s4 = 1 + 2 + 3 + 4 = 10

b. s3 = 100 + 80 + 60 = 240
s4 = 100 + 80 + 60 + 40 = 280
semoga membantu

Bab Pola Bilangan

a. S3 = 1 + 2 + 3 = 6
S4 = S3 + 4 = 6 + 4 = 10

b. a = 100
b = -20

Sn = n/2 (2a + (n - 1)b)
S3 = 3/2 (2(100) + (3 - 1)(-20))
S3 = 1,5 (200 - 40)
S3 = 240

S4 = 4/2 (2(100) + (4 - 1)(-20))
S4 = 2(200 - 60)
S4 = 280