in a geometric sequence T6=-243 & T3=72 determine the constant ratio and the sum of the first 10 terms

Answer 1

r^3 = -243/72 = (-9*27)/(9*8)
r = -3/2
a(-3/2)^2 = 72
a = 32

S10 = 32(r^10-1)/(r-1) = -11605/16