tolong jawab besert cara

a = 1
b = U2 - U1 = 3-1 = 2
Un = 99

Un = a + (n - 1)b
99 = 1 + (n - 1)2
99 = 2n - 1
99 + 1 = 2n
100 = 2n
50 = n

Sn = n/2 (a + Un)
S50 = 50/2 (1 + 99)
S50 = 25 . 100
S50 = 2500

Semoga membantu dan semoga bermanfaat...

(1+99)+(3+97)+..+(49+51)
= 100 +100+..+100
= 100 × 25 = 2500