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3 years ago

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

Mathematics

2 answers:

finlep [7]3 years ago

5 0

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

noname [10]3 years ago

5 0

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

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3 years ago

n January 1989, the temperature in Nome, Alaska dropped to −49° F. Would the gas in the driver's truck have remained in liquid f

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2 years ago

Mr. Thomas spent $1,600 of his savings on a television set and 2/5 of the remainder on a refrigerator. He had 1/3 of his origina

Katena32 [7]

Answer:

The amount spent on the refrigerator is $ 800 .

Step-by-step explanation:

Given as :

The amount spent on television = $ 1600

Le The total amount in the account = $ A

so, The amount left in account after spent on television = $ A - $ 1600

The amount spent on refrigerator = $\frac{2}{5}$ × ( A - 1600 )

The amount left in his saving account = $\frac{1}{3}$ × A

Now, According to question

A - ( 1600 + $\frac{2}{5}$ × ( A - 1600 ) ) = $\frac{1}{3}$ × A

Or, A - $\frac{1}{3}$ × A = 1600 + $\frac{2}{5}$ × ( A - 1600 )

Or, $\frac{2}{3}$ × A = 1600 + $\frac{2}{5}$ × A - $\frac{2}{5}$ × 1600

or, $\frac{2}{3}$ × A - $\frac{2}{5}$ × A = 1600 - 640

Or, $\frac{10 - 6 }{15}$ × A = 960

or, $\frac{4}{15}$ × A = 960

∴ A = $\frac{960\times 15}{4}$

I.e A = 3600

So, The amount in the saving account is $3600

∵ , The amount spent on refrigerator = $\frac{2}{5}$ × ( 3600 - 1600 )

Or, The amount spent on refrigerator = $\frac{2}{5}$ × 2000

I.e The amount spent on refrigerator = $ 800

Hence The amount spent on the refrigerator is $ 800 . Answer

4 0

4 years ago