Answer:
3
Step-by-step explanation:
first term a= 2
last term tn= 32
common ratio r= -2
number of terms
= tn=ar^n-1
32 = 2*(-2)^n-1
divide both sides by 2
32/2 = 2*(-2)^n-1/2
16 = (-2)^n-1
Then...use 16 in the power of 2
(-2)^4 = (-2)^n-1
The bases (-2), cancels out
so we have: 4 = n-1
collect like terms
4-1 = n
3 = n
n= 3
