Answer:
See solutions below
Explanation:
Given the sequence -5, 10, -20, 40...
The nth term of the GP is expressed as;
Tn = ar^n-1
a is the first term
r is the common ratio
n is the number of terms
From the sequence, a = -5
r = 10/-5 = -20/10 = -2
Substitute
Tn = -5(-2)^n-1
This gives the explicit formula
For recursive;
a1 = -5
a2 = 10 = -2(-5) = -2a1
a3 = -20 = -2(10) = -2a2
From the shown sequence, we can see that;
an = -2an-1
This gives the recursive formula
Get the 12th term;
Using the explicit formula
T12 = -5(-2)^12-1
T12 = -5(-2)^11
T12 = -5(-2048)
T12 = 10240
Hence the 12th term is 10240