Tolong bantu jawab No. 7 Please kak

7a) 2 + 4 + 6 + 8 + 10 + ... + 100

a = 2
b = 2
n = 100/2 = 50

Sn = 1/2(n)[2a + (n - 1)b]
S50 = 1/2(50)[2(2) + (50 - 1) × 2]
S50 = 25[4 + 49 × 2]
S50 = 25[4 + 98]
S50 = 25 × 102
S50 = 2550

b) -1 + 2 - 3 + 4 - 5 + 6 - 7 + 8 - ... + 100
-1 - 1 - 1 - 1 - 1 - 1 - 1 - 1 -.....(× 50)
n = 100/2 = 50

Sn = (-1) × n
S50 = (-1) × 50
S50 = -50


c) -100 - 99 - 98 - .. - 2 - 1 - 0 + 1 + 2 + ... + 97 + 98 + 99

(-99 - 98 - ...- 2 - 1 - 0 + 1 + 2 + ...+ 97 + 98 + 99)
= 0

sisa satu angka yaitu - 100

Sn = -100