Question

Find s8 for the following geometric sequence: 3, – 6, 12, – 24.

A. –238
B. –255
C. 204
D. 192

Answer 1

Step by step :
(Add number with it self) ( forget negative signs ) ( 3 is s2)
.3+3=6 (s3)
.6+6=12 (s4)
.12+12=24 (s5)
.24+24=48 (s6)
.48+48=96 (s7)
.96+96=192 (s8)

Answer 2

Answer:

$\huge{\boxed{\boxed{\sf{S8=-255}}}}$

Step-by-step explanation:

$\huge{\boxed{\boxed{\underline{\sf{SOLUTION-}}}}}$

□a=3

□common ratio=$\frac{a2}{a1}=\frac{-6}{3}=-2$

To find

○sum of 8th term of this G.P

$s8 = \frac{a( {r}^{n} - 1 )}{r - 1} \\ = ) \frac{3( {( - 2})^{8} - 1) }{ - 2 - 1} \\ = ) \frac{3(256 - 1)}{ - 3} \\ = ) \frac{3 \times 255}{ - 3} \\ = ) - 255$

$\huge{\boxed{\boxed{\sf{S8=-255}}}}$

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