Sixty-four is the product of eight and the sum of a number and six.

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

2 years ago

Consider the function,

RUDIKE [14]

Answer:

If x= 4 then f(x) = 4x -5 is 11.

Step-by-step explanation:

f(x) = 4x -5

We need to find the domain value that corresponds to the output f(x) = 11

In this question, we need to solve the expression for value of x such that the answer is 11.

if x= 3

f(3) = 4(3) -5

= 12 -5

= 7

Since we want the answer 11 so we cannot take x= 3

if x = 4

f(4) = 4(4)-5

= 16 - 5

= 11

So, if x= 4 then f(x) = 4x -5 is 11.

5 0

2 years ago

Suppose that you are holding your toy submarine under the water. You release it and it begins to ascend. The graph models the de

Likurg_2 [28]

Answer:

Domain : 0 ≤ t ≤ 3

Range : -4 ≤ d ≤ 0

Step-by-step explanation:

The graph attached models the depth of submarine as a function of time.

Points on x-axis represent the time and points on y-axis represent increase in height of the submarine.

Domain of a function is represented by the points on x-axis.

Therefore, Domain : 0 ≤ t ≤ 3

Range of function is represented by te points on y-axis.

Therefore, Range : -4 ≤ d ≤ 0

3 0

2 years ago

what is te discontinuity of the function f(x) = the quantity of x squared plus 6x plus 8 all over x plus 4?

seropon [69]

Answer:

A hole at x=-4.

Step-by-step explanation:

This is a fraction so we have to worry about division by zero.

The only time we will be dividing by 0 is when x+4 is 0.

Solving the equation

x+4=0 for x:

Subtract 4 on both sides:

x=-4

So there is either a vertical asymptote or a hole at x=-4.

These are the kinds of discontinuities we can have for a rational function.

If there is a hole at x=-4, then x=-4 will make the top zero and can be cancelled out after simplification.

If is is a vertical asymptote, x=-4 will make the top NOT zero.

Let's see what -4 for x in x^2+6x+8 gives us:

(-4)^2+6(-4)+8

16+-24+8

-8+8

0

Top and bottom are 0 when x=-4.

Let's see what happens after simplication.

We are going to factor a^2+bx+c if factorable by finding two numbers that multiply to be c and add up to be b.

So what 2 numbers together multiply to be 8 and add up to be 6.

I hoped you said 4 and 2 because (4)(2)=8 where 4+2=6.

$\frac{x^2+6x+8}{x+4}=\frac{(x+4)(x+2)}{x+4}=x+2$

We we able to cancel out that factor that was giving us x=-4 is a zero.

Therefore there is a hole at x=-4.

7 0

3 years ago

In Δ ABC, which is the included side between ∠A and ∠C?

murzikaleks [220]

The answer is B AC
because it's the 2 that connect the line between A and C

5 0

3 years ago