Question

-100-99-98-...-2-1-0+1+2+...+48+49=50

Answer 1

-100-99-98-...-2-1-0+1+2+...+48+49+50
perhatikan bahwa 1+2+...+50 akan habis dengan -1 -2 -3 - ... -50
sisanya:
-100 -99 - 98 - ... -51
a = -100
b = -99 - (-100) = 1
Un = -51
Un = a + (n - 1)b
-51 = -100 + (n - 1)
n = 51

S51 = (51/2)(2(-100) + 50(1))
= (51/2)(-200 + 50)
= (51/2)(-150)
= 51 x (-75)
= -3825 Sudah benar