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3 years ago

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Euler's formula, V – E + F = 2 relates the number of vertices V, the number of edges E, and the number of faces F of a polyhedro

n. How many faces does a polyhedron with 5 vertices and 8 edges have?

1 answer:

denis23 [38]3 years ago

8 0

V – E + F = 2

5 - 8 + F = 2

- 3 + F = 2

F = 2 + 3

F = 5

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Dont really understand how to do this

bija089 [108]

Answers:

$t_{10} = -22 \ \text{ and } S_{10} = -85$

========================================================

Explanation:

$t_1 = \text{first term} = 5\\t_2 = \text{first term}-3 = t_1 - 3 = 5-3 = 2$

Note we subtract 3 off the previous term (t1) to get the next term (t2). Each new successive term is found this way

$t_3 = t_2 - 3 = 2-3 = -1\\t_4 = t_3 - 3 = -1-3 = -4$

and so on. This process may take a while to reach $t_{10}$

There's a shortcut. The nth term of any arithmetic sequence is

$t_n = t_1+d(n-1)$

We plug in $t_1 = 5 \text{ and } d = -3$ and simplify

$t_n = t_1+d(n-1)\\t_n = 5+(-3)(n-1)\\t_n = 5-3n+3\\t_n = -3n+8$

Then we can plug in various positive whole numbers for n to find the corresponding $t_n$ value. For example, plug in n = 2

$t_n = -3n+8\\t_2 = -3*2+8\\t_2 = -6+8\\t_2 = 2$

which matches with the second term we found earlier. And,

$tn = -3n+8\\t_{10} = -3*10+8\\t_{10} = -30+8\\t_{10} = \boldsymbol{-22} \ \textbf{ is the tenth term}$

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The notation $S_{10}$ refers to the sum of the first ten terms $t_1, t_2, \ldots, t_9, t_{10}$

We could use either the long way or the shortcut above to find all $t_1$ through $t_{10}$ . Then add those values up. Or we can take this shortcut below.

$Sn = \text{sum of the first n terms of an arithmetic sequence}\\S_n = (n/2)*(t_1+t_n)\\S_{10} = (10/2)*(t_1+t_{10})\\S_{10} = (10/2)*(5-22)\\S_{10} = 5*(-17)\\\boldsymbol{S_{10} = -85}$

The sum of the first ten terms is -85

-----------------------

As a check for $S_{10}$ , here are the first ten terms:

t1 = 5
t2 = 2
t3 = -1
t4 = -4
t5 = -7
t6 = -10
t7 = -13
t8 = -16
t9 = -19
t10 = -22

Then adding said terms gets us...

5 + 2 + (-1) + (-4) + (-7) + (-10) + (-13) + (-16) + (-19) + (-22) = -85

This confirms that $S_{10} = -85$ is correct.

6 0

2 years ago

Suppose that events a and b are mutually exclusive with p(a) = ½ and p(b) = ⅓.

irina1246 [14]

No, a & b are not independent if they're mutually exclusive.

Mutually exclusive means the two events cannot occur simultaneously. So if "a" happens "b" cannot. In contrast, two events are independent if the occurrence of one has no effect on the occurrence of the other.

4 0

3 years ago

What is 1+1? Very urgent

forsale [732]

Answer:

62

Step-by-step explanation:

anything plus 1 equals 62.

Hope this helps. Have a nice day you amazing bean child.

( jk jk. It's 2)

8 0

3 years ago

Use the reference angles to find the exact value of the expression cot -11 pi/6. Do not use a calculator

laiz [17]

Answer:

$\sqrt{3}$

Step-by-step explanation:

cot(-11pi/6)=cot(-pi-5pi/6)= -cot(5pi/6)=cot(pi/6)= $\sqrt{3}$ ≈1.73

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3 years ago

Keisha wants to put 170 geraniums into 4 rows. How many will be in each row and how many will be left over?

scZoUnD [109]

There will be 42 in each row with 2 left over

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3 years ago