What is the 8th for the geometric sequence 6,561; -2,187; 729; -243; ...

1st let's calculate r the common ratio:

r = (-2187) / (6561) = (729) / (-2187) = - 1/3

Value of nth term = a₁. rⁿ⁻¹, where a₁ = 1st term and n, the rank

Value of nth term = 6561r⁸ ⁽⁻¹⁾ = 6561. (-1/3) 7

Value of nth term = - 3