Write a formulae for the general formlae sequence-2,4-8,16 ... a7. find the nterm a^n

a7

a (n) = - 2*a (n-1) [a (n-s) is previous term] or - 2 (n-1) * a (1)

a7 is equal to 24.

Step-by-step explanation:

-2, 4, - 8, 16 is geometric so we will be multiplying. let's remove the negatives and see what it looks like. 2, 4, 8, 16. It seems to be multiplying by 2. Now we add the negatives back, - 2, 4, - 8, 16. It seems the factor in which we multiply will be negative.

The formula for explicit would be, d (n-1) * a (1) and recursive would be d*a (n-1).

d is the common difference, or in this case our common factor. a (n-1) means previous term. a (1) means the first term, which is - 2. and d (n-1) is the common difference multiplied into n-1. n is the term number.

Now plug in 7 for n. I will be using explicit since I believe it is easier.

-2 (n-1) * a (1)

-2 (6) * - 2

-12 * - 2

24.

The answer to a (7) will be 24.