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1 year ago

3. Find how many numbers between 232 and 252.

Mathematics

1 answer:

igomit [66]1 year ago

7 0

Answer:

252-232=20-1=19

Step-by-step explanation:

the question said in between so you don't count the first and the last numbers

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Determine formula of the nth term 2, 6, 12 20 30,42

nalin [4]

Check the forward differences of the sequence.

If $\{a_n\} = \{2,6,12,20,30,42,\ldots\}$ , then let $\{b_n\}$ be the sequence of first-order differences of $\{a_n\}$ . That is, for n ≥ 1,

$b_n = a_{n+1} - a_n$

so that $\{b_n\} = \{4, 6, 8, 10, 12, \ldots\}$ .

Let $\{c_n\}$ be the sequence of differences of $\{b_n\}$ ,

$c_n = b_{n+1} - b_n$

and we see that this is a constant sequence, $\{c_n\} = \{2, 2, 2, 2, \ldots\}$ . In other words, $\{b_n\}$ is an arithmetic sequence with common difference between terms of 2. That is,

$2 = b_{n+1} - b_n \implies b_{n+1} = b_n + 2$

and we can solve for $b_n$ in terms of $b_1=4$ :

$b_{n+1} = b_n + 2$

$b_{n+1} = (b_{n-1}+2) + 2 = b_{n-1} + 2\times2$

$b_{n+1} = (b_{n-2}+2) + 2\times2 = b_{n-2} + 3\times2$

and so on down to

$b_{n+1} = b_1 + 2n \implies b_{n+1} = 2n + 4 \implies b_n = 2(n-1)+4 = 2(n + 1)$

We solve for $a_n$ in the same way.

$2(n+1) = a_{n+1} - a_n \implies a_{n+1} = a_n + 2(n + 1)$

Then

$a_{n+1} = (a_{n-1} + 2n) + 2(n+1) \\ ~~~~~~~= a_{n-1} + 2 ((n+1) + n)$

$a_{n+1} = (a_{n-2} + 2(n-1)) + 2((n+1)+n) \\ ~~~~~~~ = a_{n-2} + 2 ((n+1) + n + (n-1))$

$a_{n+1} = (a_{n-3} + 2(n-2)) + 2((n+1)+n+(n-1)) \\ ~~~~~~~= a_{n-3} + 2 ((n+1) + n + (n-1) + (n-2))$

and so on down to

$a_{n+1} = a_1 + 2 \displaystyle \sum_{k=2}^{n+1} k = 2 + 2 \times \frac{n(n+3)}2$

$\implies a_{n+1} = n^2 + 3n + 2 \implies \boxed{a_n = n^2 + n}$

6 0

1 year ago

How do you solve 3x+7=x

vredina [299]

3x + 7 = x

First, subtract 3x from both sides. / Your problem should look like: 7 = x - 3x
Second, simplify x - 3x to -2x. / Your problem should look like: 7 = -2x
Third, divide both sides by -2. / Your problem should look like: $\frac{7}{-2}$ = x
Fourth, simplify $\frac{7}{-2}$ to $-\frac{7}{2}$ / Your problem should look like: $- \frac{7}{2}$ = x
Fifth, switch sides. / Your problem should look like: x = $-\frac{7}{2}$

Answer as fraction: $-\frac{7}{2}$
Answer as decimal: -3.5

8 0

2 years ago

Read 2 more answers

There are 5 red marbles, 15 blue marbles, and 5 green marbles In a bag. If you reach In and randomly draw two marbles without re

puteri [66]

Answer:

A because 15 + 5 + 5 = 25. 100/25 = 4. (OWO)

Step-by-step explanation:

100% A, hope that helps :D

4 0

2 years ago

Read 2 more answers