Question

Tentukan unsur-unsur yang belum diketahui
a=8 un=32 B=4 sn=

Answer 1

Un = a+(n-1)b
32 = 8 + (n-1)4
32 = 8 + 4n-4
 4n = 32-4
  n  = 28/4 = 7
Sn = n/2 (a+Un)
S7  = 7/2 (8+32)
       = 7/2 x 40
       = 140

Answer 2

a = 8  ; Un = 32 ; b = 4
Un = a + (n - 1).b
32 = 8 + (n - 1).4
32 = 8 + 4n - 4
32 = 4 + 4n
4n = 32 - 4
4n = 28
  n = 7
Sn = .(a + Un)
     = .(8 + 32)
     = .(40)
     = 7 (20)
     = 140