Question

If the fourth term of a gwometric progression is -27/4 and the fifth term is 81/4 find a1 and r

Answer 1

• a1 = 1/4
• r = -3

Explanation:

r = a5/a4 = (81/4)/(-27/4) = -3

an = a1·r^(n-1)

-27/4 = a1·(-3)^3 = -27·a1 . . . . fill in the known numbers for n=4

(-27/4)/(-27) = a1 = 1/4