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3 years ago

Find the sum of a finite geometric sequence from n = 1 to n = 7, using the expression −4(6)n − 1.

Mathematics

1 answer:

Verizon [17]3 years ago

7 0

Answer:

Step-by-step explanation:

The formula of a sum of terms of a gometric sequence:

$S_n=a_1\cdot\dfrac{1-r^n}{1-r}$

a₁ - first term

r - common ratio

We have

$a_n=-4(6)^{n-1}$

Calculate a₁. Put n = 1:

$a_1=-4(6)^{1-1}=-4(6)^0=-4(1)=-4$

Calculate the common ratio:

$r=\dfrac{a_{n+1}}{a_n}\\\\a_{n+1}=-4(6)^{n+1-1}=-4(6)^n\\\\r=\dfrac{-4(6)^n}{-4(6)^{n-1}}=6^n:6^{n-1}\\\\\text{use}\ a^n:a^m=a^{n-m}\\\\r=6^{n-(n-1)}=6^{n-n+1}=6^1=6$

$\text{Substitute}\ a_1=-4,\ n=7,\ r=6:\\\\S_7=-4\cdot\dfrac{1-6^7}{1-6}=-4\cdot\dfrac{1-279936}{-5}=-4\cdot\dfrac{-279935}{-5}=(-4)(55987)\\\\S_7=-223948$

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3 years ago

Which is an equivalent form of the equation 2x - y = 12?

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2x-y=12
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Step-by-step explanation:

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3 years ago

Read 2 more answers

Decomponha os seguintes números a) 1.585 = b) 1.059= c) 2.440 d) 5.329 e) 8.801 f) 9.999 g) 3.718 h) 6.840 i) 7.504 j) 5.225 1)

vlada-n [284]

Answer:

a) 1.585 =1.0 + 0.5+ 0.08+0.005

b) 1.059= 1 .0+ 0.0+ 0.05+0.009

c) 2.440 = 2.0 + 0.4+ 0.04

d) 5.329= 5.0 + 0.3+ 0.02+0.009

e) 8.801 = 8.0 + 0.8+ 0.00+0.001

f) 9.999= 9.0 + 0.9+ 0.09+0.009

g) 3.718 = 3.0 + 0.7+ 0.01+0.008

h) 6.840= 6.0 + 0.8+ 0.04

i) 7.504 = 7.0 + 0.5 +0.004

j) 5.225 = 5.0 + 0.2+ 0.02+0.005

1) 4.063 = 4.0 + 0.0+ 0.06+0.003= 4+0.06+0.003

m) 2.597= 2 .0+ 0.5+ 0.09+0.007

Step-by-step explanation:

A medida que nos alejamos del punto decimal, el número de ceros aumenta y el dígito se mueve hacia la derecha.

Los valores después del decimal se denominan décimas, centésimas y milésimas.

a) 1.585 =1.0 + 0.5+ 0.08+0.005

b) 1.059= 1 .0+ 0.0+ 0.05+0.009

c) 2.440 = 2.0 + 0.4+ 0.04

d) 5.329= 5.0 + 0.3+ 0.02+0.009

e) 8.801 = 8.0 + 0.8+ 0.00+0.001

f) 9.999= 9.0 + 0.9+ 0.09+0.009

g) 3.718 = 3.0 + 0.7+ 0.01+0.008

h) 6.840= 6.0 + 0.8+ 0.04

i) 7.504 = 7.0 + 0.5 +0.004

j) 5.225 = 5.0 + 0.2+ 0.02+0.005

1) 4.063 = 4.0 + 0.0+ 0.06+0.003= 4+0.06+0.003

m) 2.597= 2 .0+ 0.5+ 0.09+0.007

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