Question

What is the equation for a geometric sequence with a first term of 3 and a second term of −9? an = 3(−12)n − 1 an = 3(12)n − 1 an = 3(−3)n − 1 an = 3(3)n − 1?

Answer 1

an=a1r^n-1
a2=a1r
-9=3r
so r = -3

then an=3(-3)^n-1