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

(1 - 2) + (3 - 4) + ... + (99 - 100) --> 100 suku
= (-1) × 100/2
= -50

kalau manual jawabannya -50



kalau pake cara
n bilangan ganjil = 50 (positif)
n bilangan genap = 50 (negatif)

ganjil :
U₅₀ = 1 + (50-1)2
      = 1 + 100 - 2
      = 99

S₅₀ = 50/2 x 99
S₅₀= 2475

genap :
U₅₀ = -2 + (50-1)(-2)
      = -2 + -100 + 2
      = -100
S₅₀ = 50/2 x -100
S₅₀ = -2500

jadi =2475 + (-2500) = -25 (kok beda,, dimana kk letak kesalahannya)