tolong jawab pakai cara

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

Pembahasan :
1 + 2 + 3 + ... + 99
= S99
= 99/2(1 + 99)
= 99/2(100)
= 99(50)
= 4950

————————————————
-97 - 96 - 95 - ... + 103

Un = 103
a + (n - 1)b = 103
-97 + (n - 1) = 103
n - 98 = 103
n = 201

Sn = n/2(a + Un)
S201 = 201/2(-97 + 103)
S201 = 201/2(6)
S201 = 201(3)
S201 = 603 —» Hasil akhir