Question

@Ankh

A(n)=-2x2
A.-8;-64;-1,024
B. 1; -64;-16,384
C. -2;-16;-256
D. -4;-32;-512

Answer 1

is that an x or a "times"

what is the question?

Answer 2

times and find the first, fourth, and eighth terms of the sequence

Answer 3

@zzr0ck3r

Answer 4

\[a_n=-2 \times 2\]
We know that the equation for a geometric progression is:
\[a_n = a_1 \times q^{n-1}\]
So for -2x2 to occur n must be 1, since:
\[x^1 = x\]
So just from this we know that:
\[a_1 = -2\]
And:
\[q = 2\]

Answer 5

(correction) So for -2x2 to occur n must be 2

Answer 6

We can plug in to test that the 4th and 8th terms of sequence apply and that the answer is indeed C.
\[a_4 = -2 \times 2^{4-1} = -16\]
\[a_8 = -2 \times 2^{8-1} = -256\]

Answer 7

But be careful because: \[a \times b = b \times a\]
So check if it isn't:
\[a_n = 2^{n-1} \times -2\]
That way a1 = 2, and we have no answer that starts with 2, so C can safely be chosen as the right one.