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3 years ago

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Start time 7:41 elapsed time dont no and ending time 8:50

2 answers:

Makovka662 [10]3 years ago

7 0

109 seconds is the answer

mr_godi [17]3 years ago

5 0

109 seconds!! I hope this helped!

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Find the indicated nth partial sum of the arithmetic sequence.<br> −7, −3, 1, 5, . . ., n = 30

TiliK225 [7]

Step-by-step explanation:

Given the Arithmetic sequence

$-7, -3, 1, 5, . . .$

An arithmetic sequence has a constant difference d and is defined by

$a_n=a_1+\left(n-1\right)d$

$\mathrm{Compute\:the\:differences\:of\:all\:the\:adjacent\:terms}:\quad \:d=a_{n+1}-a_n$

$-3-\left(-7\right)=4,\:\quad \:1-\left(-3\right)=4$

$\mathrm{The\:difference\:between\:all\:of\:the\:adjacent\:terms\:is\:the\:same\:and\:equal\:to}$

$d=4$

$\mathrm{The\:first\:element\:of\:the\:sequence\:is}$

$a_1=-7$

as

$a_n=a_1+\left(n-1\right)d$

$\mathrm{Therefore,\:the\:}n\mathrm{th\:term\:is\:computed\:by}\:$

$a_n=4\left(n-1\right)-7$ ∵ $d=4$

$\mathrm{Arithmetic\:sequence\:sum\:formula:}$

$n\left(a_1+\frac{d\left(n-1\right)}{2}\right)$

$\mathrm{Plug\:in\:the\:values:}$

$n=30,\:\space a_1=-7,\:\spaced=4$

$=30\left(-7+\frac{4\left(30-1\right)}{2}\right)$

$=30\left(58-7\right)$ ∵ $\frac{4\left(30-1\right)}{2}=58$

$=30\cdot \:51$

$=1530$ ∵ $\mathrm{Multiply\:the\:numbers:}\:30\cdot \:51=1530$

Therefore, the indicated nth partial sum of the arithmetic sequence is 1530.

ANOTHER METHOD

as

$a_n=4\left(n-1\right)-7$

n = 30

$\sum _{n=1}^{30}\:4\left(n-1\right)-7$

$=\sum _{n=1}^{30}4n-11$

$\mathrm{Apply\:the\:Sum\:Rule}:\quad \sum a_n+b_n=\sum a_n+\sum b_n$

$=\sum _{n=1}^{30}4n-\sum _{n=1}^{30}11$

as

$\sum _{n=1}^{30}4n=1860$

and

$\sum _{n=1}^{30}11=330$

so

$=1860-330$

$=1530$

7 0

4 years ago

IM GIVING OUT BRAINLIEST!!!<br><br> 9*8+2+4=_______

inn [45]

We use the Order of Operations here.

Parentheses

Exponents

Multiplying

Adding

Dividing

Subtracting (PEMDAS)

And if both are there, we work left to right.

In the process we multiply first, then add left to right..

So,

9 * 8 + 2 + 4

= 72 + 2 + 4

= 74 + 4

= 78.

3 0

3 years ago

Read 2 more answers

If 20 articles cost $90,then the cost of 9 articles is

Tom [10]

Answer:

$40.50

Step-by-step explanation:

90 divided by 20 is 4.5. then you multiply that times 9 and that's your answer.

8 0

3 years ago

PLEASEEEE FACTOR THIS

Tanzania [10]

= (7a + 2b)(7a + 2b)
= (7a +2b)^2

3 0

3 years ago

Solve for x. (12x + 4) - 8 = 12 A) 30 B) 33 C) 36 D) 40

Andru [333]

Steps to solve:

(12x + 4) - 8 = 12

~Combine like terms

12x - 4 = 12

~Add 4 to both sides

12x = 16

~Divide 12 to both sides

x = 16/12 or x = 4/3

Best of Luck!

8 0

3 years ago