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valentina_108 [34]

3 years ago

9

I really need help in this 7th grade math

1 answer:

Rasek [7]3 years ago

4 0

Answer:

the awnser is 28

Step-by-step explanation:

the little 2 mean you times the 3 by it so it's 1+6. which is 7 and 18+2 is 20 and 20+7 is 28

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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

In triangle JKL, m of angle J = 90, m of angle K = 30, and m of angle L = 60. Which of the following statements about triangle J

Lynna [10]

Answer:

option C. $KL=2*JL$

option D. $JK=\frac{\sqrt{3}}{2}*KL$

option F. $JK=\sqrt{3}*JL$

Step-by-step explanation:

step 1

we know that

In the right triangle JKL

$sin(30\°)=\frac{JL}{KL}$

$sin(30\°)=\frac{1}{2}$

so

$\frac{1}{2}=\frac{JL}{KL}$

$KL=2*JL$

step 2

$cos(30\°)=\frac{JK}{KL}$

$cos(30\°)=\frac{\sqrt{3}}{2}$

so

$\frac{\sqrt{3}}{2}=\frac{JK}{KL}$

$JK=\frac{\sqrt{3}}{2}*KL$

step 3

$tan(30\°)=\frac{JL}{JK}$

$tan(30\°)=\frac{1}{\sqrt{3}}$

$\frac{1}{\sqrt{3}}=\frac{JL}{JK}$

$JK=\sqrt{3}*JL$

7 0

4 years ago

Please help me asap!!!!

Ghella [55]

Milli = .001
deci = .01
centi = 1
kilo = 1000

6 0

4 years ago

First determine if the given is a ordered pair (-1.7): 4x + y = 3. 2x-y=3

Mrrafil [7]

Answer:

i didnt mean to click on this and it wont let me exit out im sorry

Step-by-step explanation:

4 0

3 years ago

Is this correct i im not sure :(

forsale [732]

Answer:

Not sure exactly were they go, but i can tell you that 5/6 goes between 0 and 1. Since its not a mixed fraction it cant possibly be over at 5. Like i said sorry i couldn't say exactly were to put them.

Step-by-step explanation:

6 0

3 years ago

Read 2 more answers