Question

Jika suku pertama suatu barisan geometric 16 Dan suku ke tiga 36 maka jumlah Lima suku pertama adalah..?

Answer 1

A = 16
u3... ar^2 = 36

a r^2 = 36
16 x r^2 = 36
r^2 = 36/16
r  = 6 / 4 = 3/2

S5 = a ( r^5 - 1 ) / r -1
      = 16 ( (3/2)^5 - 1) / 3/2 - 2/2
      = 16 ( 243/32 - 32/32 ) /  1/2
    = 16 ( 211 / 32) x 2/1
    =  32 ( 211/32)
     = 211