Jumlah 50 suku pertama deret -98,-95,-92,-89... adalah.... a.-1.552 b.-1.225 c.-1.035 d.1.025

Sn = n/2 (2a+(n-1)b)
S50 = 50/2 (2 × -98) + 49×3
= 25 (-196 + 147)
= 25(-49)
= -1225 (B)

Bab Barisan dan Deret
Matematika
Kelas 9 SMP

Barisan Aritmatika

b = -95 - -98
   = -95 + 98
   = 3

U50 = -98 + (50 - 1) 3
        = -98 + 147
        = 49

S50 = 50/2 (-98 + 49)
       = 25 (-49)
       = -1225 (B)

Semoga Membantu!!!