Question

Find the 8th term of the geometric sequence 7,−21,63,

Answer 1

Answer:

8th term is -15309

Step-by-step explanation:

${ \boxed{ \bf{u_{n} = a( {r}^{n - 1} ) }}} \\ { \tt{u_{8} = 7( {( - 3)}^{8 - 1}) }} \\ { \tt{u_{8} = 7( - 2187)}} \\ { \tt{u _{8} = - 15309}}$

r is the common difference, r = -21/7 = -3

Answer 2

Answer:

a₈ = - 15309

Step-by-step explanation:

The nth term of a geometric sequence is

$a_{n}$ = a₁ $(r)^{n-1}$

where a₁ is the first term and r the common ratio

Here a₁ = 7 and r = $\frac{a_{2} }{a_{1} }$ = $\frac{-21}{7}$ = - 3 , then

a₈ = 7 × $(-3)^{7}$ = 7 × - 2187 = - 15309