tentukan hasil dr 1-2+3-4+5-6+7-8+...-100 -100-99-98-...-2-1-0+1+2+...+48+49+50

Mapel : Matematika
Kelas : IX SMP
Bab : Barisan dan deret

Pembahasan :
1 - 2 + 3 - 4 + ... - 100
= -1 - 1 - 1 - .... - 1
= - (1 + 1 + 1 + ...)
= - (100/2)
= -50

————————————————
-100 - 99 - 98 - ... + 50

Un = a + n - 1
50 = -100 + n - 1
50 = n - 101
n = 151

Sn = n/2(a + Un)
S151 = 151/2(-100 +50)
S151 = 151/2(-50)
S151 = 151(-25)
S151 = -3775 —» Hasil akhir