Question

What is the 10th term of the geometric sequence –1, 3, –9, …?

Answer 1

y isnt it negative?

Answer 2

See the pattern. The first, third, fifth(odd positions) are negative and even positions are positive

Answer 3

since this is a geometric series, you know that, between each term, there is a constant ratio, so 3/-1 = -9/3 = -3. Now I did a big mistake on my first answer here. First term is (-1)*(-3)^0, which is different.

The reason why the -1 is because, for an even exponent, you should have a position answer, but you don't and vise-versa for an odd exponent (think -2 * -2 = 4 and -2 * -2 * -2 = -8). Since the signs are inverse, you need the -1 (-2 * -2 * -1 =-4 and -2* -2* -2* -1 = 8)

The formula for this is then (-1) * (-3)^(n-1), n being the term where you are. To check, just plug in one that you already know (i.e. 3rd term) and validate that it works

Answer 4

I AM SORRY AGAIN. LAST TIME PLEASE. THE ANSWER IS 19683 not negative...