I NEED HELP PLEASE!
Khalid wrote the sequence below.
x-1, -2x+2, 4x-4, -8x+8
Which formula can be used to find the 10th term of the sequence?
A. [tex]a10=(x-1)*(-2)^1^0^-^1[/tex]
B. [tex]a10=(x-1)^1^0^-^1[/tex]
C. [tex]a10=(x-1)*(2)^1^0^-^1[/tex]
D. [tex]a10=(x-1)*(-2)^1^0[/tex]

Respuesta :

The given sequence is x-1, -2x+2, 4x-4, -8x+8 .

Notice that this is a geometric sequence because here we have equal common ratio.

So, common ratio : r = [tex] \frac{a_{2}}{a_{1}} [/tex]

= [tex] \frac{-2x+1}{x-1} [/tex]

= [tex] \frac{-2(x-1)}{(x-1)} [/tex]Take out -2 as common factor

= -2 Cancel out x - 1.

The formula for general term of a geometric sequence is,

[tex] a_{n} =a_{1} r^{n-1} [/tex]

Where, first term: [tex] a_{1} =x-1 [/tex]

We need to find the 10th term of this sequence. So, n = 10.

Next step is to plug in these values in the above formula to get the 10th term. Hence,

[tex] a_{10} = (x -1)(-2)^{10-1} [/tex]

So, A is the correct choice.