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Sergeu [11.5K]
2 years ago
13

Find a formula for the sum of the first n even integers : 2 + 4 + 6 + ... + 2n.

Mathematics
1 answer:
Sedbober [7]2 years ago
7 0

Let S be the sum,

S = 2 + 4 + 6 + ... + 2 (n - 2) + 2 (n - 1) + 2n

Reverse the order of terms:

S = 2n + 2 (n - 1) + 2 (n - 2) + ... + 6 + 4 + 2

Add up terms in the same positions, so that twice the sum is

2S = (2n + 2) + (2n + 2) + (2n + 2) + ... + (2n + 2)

or

2S = n (2n + 2)

Divide both sides by 2 to solve for S :

S = n (n + 1)

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At a museum cafe you can get a pre-made boxed lunch with a sandwich, fruit, and drink for only . The sandwiches are made with ei
slamgirl [31]

Answer:

1/8 or 0.125

Step-by-step explanation:

So, I started solving this problem by writing all the possible options, then pairing them each up with a fruit and drink..

...But when I read the question again, I noticed I forgot to leave out the fruit, as this question states that you're trying to retrieve "a turkey sandwich and a bottle of water.."

Well, oof.

Despite that, I'm still giving this answer as if it never left out the fruit. So, let's see what we need to do.

To find all the possible lunch options, I started out by writing down one of our meats, Turkey. As per requested, I made every possible turkey combination that included a fruit and drink, which gave me this:

  • Turkey, apple and water
  • Turkey, orange and water
  • Turkey, orange and juice
  • Turkey, apple and juice

Same for the ham:

  • Ham, apple and water
  • Ham, apple and juice
  • Ham, orange and juice
  • Ham, orange and water

Putting these together, this gives up 8 different lunchbox combinations. If we're trying to get one and we randomly select it, then we have a 1/8 chance of grabbing the turkey sandwich and a bottle of water....

..and a fruit.

Hope this helped!

If you need me to show my work, just comment me and I will attach a screenshot!

Source: N/A

5 0
3 years ago
There is a group of 5 turtles near the playground. More turtles joined. Now there are 13 turtles. How many turtles joined the gr
ivann1987 [24]

Answer:

8 turtles joined the group

Step-by-step explanation:

13-5=8

6 0
2 years ago
5 + n2 &gt; 8<br> A. n &gt; 6<br> B. n&gt;3<br> C. n&gt;1.5<br> D. n &lt; 26
san4es73 [151]
N•2>8
then dive both sides 2n>8
and get n>4
4 0
3 years ago
Read 2 more answers
There were three quizzes for the week. The first quiz was worth twice as much as the second quiz. The third quiz was 10 points l
iren2701 [21]
X+y+z=70
x=2y
z=2y-10
6 0
3 years ago
Solve:<br> 2/3x+15=17<br><br> 3x+8-x=7<br><br> 4(2x-6)=2
Volgvan

Answer:

x = 3

x = (-1)/2

x = 13/4

Step-by-step explanation:

Solve for x:

(2 x)/3 + 15 = 17

Put each term in (2 x)/3 + 15 over the common denominator 3: (2 x)/3 + 15 = (2 x)/3 + 45/3:

(2 x)/3 + 45/3 = 17

(2 x)/3 + 45/3 = (2 x + 45)/3:

1/3 (2 x + 45) = 17

Multiply both sides of (2 x + 45)/3 = 17 by 3:

(3 (2 x + 45))/3 = 3×17

(3 (2 x + 45))/3 = 3/3×(2 x + 45) = 2 x + 45:

2 x + 45 = 3×17

3×17 = 51:

2 x + 45 = 51

Subtract 45 from both sides:

2 x + (45 - 45) = 51 - 45

45 - 45 = 0:

2 x = 51 - 45

51 - 45 = 6:

2 x = 6

Divide both sides of 2 x = 6 by 2:

(2 x)/2 = 6/2

2/2 = 1:

x = 6/2

The gcd of 6 and 2 is 2, so 6/2 = (2×3)/(2×1) = 2/2×3 = 3:

Answer:  x = 3

______________________________________________________

Solve for x:

3 x - x + 8 = 7

Grouping like terms, 3 x - x + 8 = (3 x - x) + 8:

(3 x - x) + 8 = 7

3 x - x = 2 x:

2 x + 8 = 7

Subtract 8 from both sides:

2 x + (8 - 8) = 7 - 8

8 - 8 = 0:

2 x = 7 - 8

7 - 8 = -1:

2 x = -1

Divide both sides of 2 x = -1 by 2:

(2 x)/2 = (-1)/2

2/2 = 1:

Answer: x = (-1)/2

_______________________________________

Solve for x:

4 (2 x - 6) = 2

Divide both sides of 4 (2 x - 6) = 2 by 4:

(4 (2 x - 6))/4 = 2/4

4/4 = 1:

2 x - 6 = 2/4

The gcd of 2 and 4 is 2, so 2/4 = (2×1)/(2×2) = 2/2×1/2 = 1/2:

2 x - 6 = 1/2

Add 6 to both sides:

2 x + (6 - 6) = 1/2 + 6

6 - 6 = 0:

2 x = 1/2 + 6

Put 1/2 + 6 over the common denominator 2. 1/2 + 6 = 1/2 + (2×6)/2:

2 x = 1/2 + (2×6)/2

2×6 = 12:

2 x = 1/2 + 12/2

1/2 + 12/2 = (1 + 12)/2:

2 x = (1 + 12)/2

1 + 12 = 13:

2 x = 13/2

Divide both sides by 2:

x = (13/2)/2

2×2 = 4:

Answer: x = 13/4

8 0
3 years ago
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