1+3+5+7+9+...+99 1-2+3-4+5-6+7-8+...- 100

Bab Bilangan Bulat

1. U1 = 1
U2 = 3
U3 = 5
...
Un = 2n - 1
99 = 2n - 1
99 + 1 = 2n
n = 100/2
n = 50

S = 1 + 3 + 5 + ... + 99
S = 99 + 97 + 95 + ... + 1
__________________ +
2S = 100 + 100 + 100 + ... + 100 [Sebanyak 50 kali]
S = (50 × 100)/2
S = 2.500

2. 1 - 2 + 3 - 4 + 5 - ... - 100
= 1 + 99 - 2 - 98 + 3 + 97 - ... - 100
= 100 - 100 + 100 - 100 + ... - 50 - 100

+100 sebanyak 25
-100 sebanyak 25

= 25 × 100 + 25 × (-100) - 50
= 2.500 - 2.500 - 50
= -50