Emergency help please thank you

Find the nth term of the sequence 7,25,51,85,127

olya-2409 [2.1K]

Let a (n) denote the n-th term of the given sequence.

Check the forward differences, and denote the n-th difference by b (n). That is,

b (n) = a (n + 1) - a (n)

These so-called first differences are

b (1) = a (2) - a (1) = 25 - 7 = 18

b (2) = a (3) - a (2) = 51 - 25 = 26

b (3) = a (4) - a (3) = 85 - 51 = 34

b (4) = a (5) - a (4) = 127 - 85 = 42

Now consider this sequence of differences,

18, 26, 34, 42, …

and notice that the difference between consecutive terms in this sequence b is 8:

26 - 18 = 8

34 - 26 = 8

42 - 34 = 8

and so on. This means b is an arithmetic sequence, and in particular follows the rule

b (n) = 18 + 8 (n - 1) = 8n + 10

for n ≥ 1.

So we have

a (n + 1) - a (n) = 8n + 10

or, replacing n + 1 with n,

a (n) = a (n - 1) + 8 (n - 1) + 10

a (n) = a (n - 1) + 8n + 2

We can solve for a (n) by iteratively substituting:

a (n) = [a (n - 2) + 8 (n - 1) + 2] + 8n + 2

a (n) = a (n - 2) + 8 (n + (n - 1)) + 2×2

a (n) = [a (n - 3) + 8 (n - 2) + 2] + 8 (n + (n - 1)) + 2×2

a (n) = a (n - 3) + 8 (n + (n - 1) + (n - 2)) + 3×2

and so on. The pattern should be clear; we end up with

a (n) = a (1) + 8 (n + (n - 1) + … + 3 + 2) + (n - 1)×2

The middle group is the sum,

$\displaystyle 8\sum_{k=2}^nk=8\sum_{k=1}^nk-8=\frac{8n(n+1)}2-8=4n^2+4n-8$

so that

a (n) = a (1) + (4n ² + 4n - 8) + 2 (n - 1)

a (n) = 4n ² + 6n - 3

4 0

3 years ago

Tell whether the data in the table can be modeled by a linear equation. Explain.

anastassius [24]

Answer:

y = -3x + 7

Step-by-step explanation:

Choosing two points from the given table:

Let (x1, y1) = (-3, 16)

(x2, y2) = (-1, 10)

Plug these given values into the slope formula:

m = (y2 - y1)/(x2 - x1)

= (10 - 16) / (-1 - (-3))

= -6 / (-1 + 3)

= -6/2

= -3

Therefore, the slope is -3.

Next, choose one of the points and plug into the point-slope form:

Let's use (-1, 10) as (x1, y1):

y - y1 = m(x - x1)

y - 10 = -3(x - (-1))

y - 10 = -3(x + 1)

y - 10 = -3x - 3

Add 10 on both sides to isolate y:

y - 10 + 10 = -3x - 3 + 10

y = -3x + 7

8 0

2 years ago

Calculate the mean number of students per class at watch school. Write your answers in sentences that explain what the means rep

Tpy6a [65]

To find the mean you add all the numbers then divide the sum by how many numbers there are :

1)Ford School

21+19+20=60

there are 3 numbers in the equation so you divide 60 by 3 :

60÷3=20

the mean for Ford School is 20

2)Carter School

41+36+37=114

there are 3 numbers in the equation so you divide 114 by 3 :

114÷3=38

the mean for Carter School is 38

hope this helps

6 0

2 years ago

Read 2 more answers

Jorge bought 6 large balloons for a party. This was 25% of all the balloons he bought. How many total balloons did Jorge buy sho

riadik2000 [5.3K]

Answer:

The answer would be 24 balloons in total.

Step-by-step explanation:

Jorge bought 6 large balloons, which was 25% of ALL the balloons he bought.

Meaning that since 6 is 25% of the number 24, he bought 24 balloons in total.

PROOF:

25% * 24 = 6

24 / 6 = 4

6 * 4 = 24

<h2>Mark me Brainliest Please.</h2>

8 0

2 years ago

What is y=3x^2-2 in vertex form

Nata [24]

$\bf \qquad \qquad \textit{parabola vertex form}
\\\\\\
y=a(x-{{ h}})^2+{{ k}}\\
x=a(y-{{ k}})^2+{{ h}}\qquad\qquad vertex\ ({{ h}},{{ k}})\\\\
-----------------------------\\\\
y=3x^2-2\iff y = 3(x-0)^2-2$

3 0

3 years ago