Question

What is the equation for a geometric sequence with a first term of 5 and a second term of −10?

an = 5(−2)n − 1
an = 5(2)n − 1
an = 5(−15)n − 1
an = 5(15)n − 1

Answer 1

Answer: A is correct, an = 5(−2)n − 1

Explanation:

The formula for geometric sequences is an=a(r)^n-1

a is the first term, which is 5 in this case

r is the common ratio, which is -2 because (5)(-2)=-10