What is the ninth term of the following geometric sequence?

Question

a4=27
a7=64
a9=

Answer 1

a+3d = 27
a+6d = 64
subtract them
3d = 37
d = 37/3

a + 3(37/3) = 27
a = -10

term(9) = a+8d
= -10 + 8(37/3) = 266/3

check:
term(4) = a+3d = -10 + 3(37/3) = 27
term(7) = a+6d = -10 + 6(37/3) = 64