u1=5 u6=55 tentukan S16

mencari b
u1 = a + b = 5
u6 = a + 5b = 55
(di kurang)

-5 = -50
b = -50/-5
b =10


mencari a
a + 5b =55
a + 5.10 =55
a + 50 = 55
55 - 50 = 5


masukkan rumus
n/2 (2.a + (n-1) ×b)
=16/2 (2.5 + (16-1) × 10)
=8 (10 + 15 × 10)
=8 (160)
=1280

Bab Barisan dan Deret
Matematika SMP Kelas IX

Aritmatika
b = (U6 - U1)/(6 - 1)
   = (55 - 5) / 5
   = 10

Un = a + (n - 1) b
U16 = 5 + (16 - 1) x 10
U16 = 5 + 15 x 10
U16 = 5 + 150
U16 = 155

Sn = (n/2) x (U1 + Un) 

S16 = (16/2) x (5 + 155)
        = 8 x 160
        = 1.280