Let S1= 1, S2=2+3, S3= 4+5+6
Find S7
Find S17
Find Sn
Answer:
S7 = 175S17 = 2465Sn = 1/2(n³ +n)Step-by-step explanation:
The progression of sums is ...
1, 5, 15, 34, 65, ...
So, first differences are ...
4, 10, 19, 31
Second differences are ...
6, 9, 12, ...
Third differences are constant:
3, 3, ...
This means the expression for Sn will be a cubic expression. If dn is the first of the n-th differences, then the equation can be written as ...
Sn = S1 +(n -1)(d1 +(n -2)/2(d2 +(n -3)/3(d3)))
And this simplifies a little bit to ...
Sn = 1 +(n -1)(4 +(n -2)(n +3)/2)
In simpler form, we have ...
Sn = 1/2(n³ +n)
Then the two terms we're interested in are ...
S7 = (1/2)(7³ +7) = 175
S17 = (1/2)(17³ +17) = 2465
Each term Sₙ consists of the sum of a triangular number of terms, which are given by
[tex]T_n = \displaystyle \sum_{k=1}^n k = 1 + 2 + 3 + \cdots + n = \frac{n(n+1)}2[/tex]
The triangular numbers are given recursively for n ≥ 1 by
[tex]T_n = T_{n-1} + n[/tex]
starting with T₀ = 0.
For example,
• S₁ = 1 and
[tex]\displaystyle S_1 = \sum_{k=T_0+1}^{T_1} k = \sum_{k=1}^1 k = 1[/tex]
• S₂ = 2 + 3 and
[tex]\displaystyle S_2 = \sum_{k=T_1+1}^{T_2} k = \sum_{k=2}^3 k = 2 + 3[/tex]
• S₃ = 4 + 5 + 6 and
[tex]\displaystyle S_3 = \sum_{k=T_2+1}^{T_3} k = \sum_{k=4}^6 k = 4 + 5 + 6[/tex]
Then the n-th term of the sequence we're considering is
[tex]S_n = \displaystyle \sum_{k=T_{n-1}+1}^{T_n} k = \sum_{k=T_{n-1}+1}^{T_{n-1}+n} k[/tex]
Expanding this sum, we have
[tex]S_n = \left(T_{n-1}+1\right) + \left(T_{n-1}+2\right) + \left(T_{n-1}+3\right) + \cdots + \left(T_{n-1}+n\right)[/tex]
There are n terms on the right side, and hence n copies of [tex]T_{n-1}[/tex], and the rest of the terms make up the next triangular number [tex]T_n[/tex] :
[tex]S_n = nT_{n-1} + 1 + 2 + 3 + \cdots + n[/tex]
[tex]S_n = nT_{n-1} + \displaystyle \sum_{k=1}^n k[/tex]
[tex]S_n = nT_{n-1} + T_n[/tex]
We have a closed form for [tex]T_n[/tex], so we end up with
[tex]S_n = n \cdot \dfrac{(n-1)n}2 + \dfrac{n(n+1)}2 \implies \boxed{S_n=\dfrac{n^3+n}2}[/tex]
From here it's easy to find S₇ and S₁₇.
[tex]S_7 = \dfrac{7^3+7}2 \implies \boxed{S_7 = 175}[/tex]
[tex]S_{17} = \dfrac{17^3+17}2 \implies \boxed{S_{17} = 2465}[/tex]
Dog food is sold in 7 pound bags. Sketch
a graph to show the weight of dog food
purchased by a customer who buys 0, 1, 2, 3, or 4 bags. Tell whether the graph is continuous or discrete.
Answer:
Continuous
Step-by-step explanation:
Describe what is meant by the operation of division using the terms dividend , divisor , and quotient
Answer:
Dividend: Number on top
Divisor: Number on bottom
Quotient: Answer
Dividend ÷ Divisor = Quotient
HELP ME!! (I WILL GIVE BRAINLIEST!)
Answer:
|-5| absolute be always + so 5
Answer:
[tex]5[/tex]
Step-by-step explanation:
Step 1: Determine what absolute value does
Taking the absolute value of a number just returns how far a specific value is from 0. So in this case we see a number -9 and although it's negative it's still 9 away from 0 therefore that would be the absolute value.
We are missing the absolute value of -5 or 5 so we know that taking the absolute value would just give us the distance from 0. In this case that would just be 5.
Answer: [tex]5[/tex]
Multiple 120 by 5.
1) 60, 2) 125, 3) 600, 4) 1205
Answer: the answer is 600 or the letter C
Answer:
3) 600
Step-by-step explanation:
5 x 0 = 05 x 2 = 10 put the 1 from the ten on top of the 1 in 1205 x 1 = 55 + 1 = 6answer 600Minh spent $3.50 on 25 stickers.
How much did each sticker cost?
Answer:
0.14
Step-by-step explanation:
brainliest please
please help with this!!!!
Answer:
6311000
Step-by-step explanation:
The first thing we do is calculate the total amount of people in both states. 6.89 x10 raised to the 6th power is equal to 6890000. Then we multiply 5.79 by 10 to the fifth power, which equals to 579000. Then we subtract the numbers, and get 6311000. They want you to answer in standard notation, which is the regular way of writing numbers such as 10, instead of 10^1.
The difference in population
[tex] = (6.89 \times {10}^{6} ) - (5.79 \times {10}^{5} ) \\ = (6.89 \times 10 \times {10}^{5} ) - (5.79 \times {10}^{5} ) \\ = (68.9 \times {10}^{5} ) - (5.79 \times {10}^{5} ) \\ = (68.9 - 5.79) \times {10}^{5} \\ = 63.11 \times {10}^{5} [/tex]
Answer:
[tex]63.11 \times {10}^{5} [/tex]
Hope you could get an idea from here.
Doubt clarification - use comment section.
Given the function, f(x) = x ^ 2 + 9x , find f(- 7)
you walk 3/4 miles to a grocery store. Then you walk another 1/5 miles to a shoe store. How many miles have you walked in all?
Answer:
19/20 miles
Step-by-step explanation:
3/4 + 1/5
3/4 = 0.75
1/5 = 0.2
3/4 + 1/5
= 0.75 + 0.2
= 0.95
= 95/100
= 19/20
Therefore,
the miles you have walked in all is 19/20.
If a triangle has a base of 6' and a height of 4' its area would be what?
A= bxh 2
A= 6x4 2
A= 12 sq. ft.
Answer:
Hello There!
According to the question,
Base=6
And
Height =4
Let's know the formula
[tex] \frac{1}{2} \times base \times height \\ so \\ \frac{1}{2} \times 6 \times 4 \\ [/tex]
simplify 2 with 6 then it will look like this
[tex] \frac{1}{1} \times3 \times 4 \\ \\ [/tex]
1 has no value so
[tex]3 \times 4 = 12 {ft}^{2} \\ [/tex]
So third option
[tex]a = 12 {ft}^{2} [/tex]
is correct.
[tex]\Large\textsf{Hope \: It \: Helped}[/tex]
Answer:
Area = 12 sq ft
Step-by-step explanation:
The formula to find the area of a triangle is
1/2 bh so we will replace the letters with their number value
1/2 (6x4)
1/2 x 24 = 12
So, 12 is your answer!
Jen is on the platform of her boat. She sights the top of a lighthouse at an angle of 30º as shown below. She knows that the height of the lighthouse is 50 meters.
How far is Jen from the base of the lighthouse, in meters?
The distance Jen is from the base of the lighthouse is 86.6 meters.
Trigonometric ratio is used to show the relationship between the sides of a and angles of a right angled triangle.
Let d represent the distance Jen is from the base of the lighthouse.
Using trigonometric ratios:
[tex]tan(30)=\frac{50}{d} \\\\d=\frac{50}{tan(30)} \\\\d=86.6\ m[/tex]
The distance Jen is from the base of the lighthouse is 86.6 meters.
Find out more on Trigonometric ratio at: https://brainly.com/question/10417664
Help me with this question
Answer:
LETS
GO
BRANDON
Step-by-step explanation:
Find the value of a
I’m decided go between 40 and 6.4
Is this relation a function?
(-1,2) (1,17) (3,-4) (1,20)
The group of points {(0, 1), (0, 5), (2, 6), (3, 3)} is not a function, but the group of points {(1, 4), (2, 7), (3, 1), (5, 7)} is a function. What do you notice about the two groups of points? What do you think it means to be a function?
You can use the definition of a function to classify which mapping is a function and which mapping is not a function.
The first group is not a function as there are two outputs for 0
The second group is a function as there are single output to each input.
What is a function?There are two sets of values. When we connect first set's values with other set, it is called mapping one set's value to other set. All type of mappings are called relations.
Such relations which are such that each element of the first set(also called input set or domain) is mapped to only one value of the other set(called codomain, and if all values are occupied, then called range or output set), then such relation is called function.
So, for a mapping to be function, we need each input to be mapped to only one output.
Using above definitionFor group 1, we see that 0 has output 1 and output 5 both. Since for a mapping to be a function, we need each input to have single output, thus, this group doesn't represent a function.
For group 2, we see that each input has only one output, thus,this group represents a function.
Remember that we assumed that the pair of points were written as
(input, output)
Thus.
The first group is not a function as there are two outputs for 0
The second group is a function as there are single output to each input.
Learn more about functions here:
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A man walks 10 km, then travels a certain distance by train and then by bus as far as twice by the train. If the whole journey is of 70km, how far did he travel by train?
Answer:
The man traveled 20km by train.
Step-by-step explanation:
If x is the distance he traveled by train, you can write this equation to represent the situation:
[tex]10+x+2x=70[/tex]
Then, you can simply solve for x:
[tex]10+3x=70\\3x=60\\x=20[/tex]
The man traveled 20km by train.
[tex]10+(20)+2(20)=70\\10+20+40=70\\70=70[/tex]
Plsss helpp no links plss
Answer:
arrange them: -9x^3+2x^3-4x^2+x^2-6x-5x
the simplified is: -7x^3-3x^2-11x
find the following right triangle, find the side length x
Answer:
x=41
Step-by-step explanation:
9²+40²=x²
81+1600=x²
1681=x²
√1681=√x²
41=x
identify a possible explicit rule for the nth term of the sequence 9, 17, 25, 33, 41
Answer:
The explicit formula for the nth term of the sequence is [tex]a_n=9+8(n-1)[/tex]
Step-by-step explanation:
Recall:
The explicit formula for a sequence is [tex]a_n=a_1+(n-1)d[/tex] where [tex]a_n[/tex] is the [tex]n[/tex]th term, [tex]a_1[/tex] is the first term, and [tex]d[/tex] is the common difference
Given:
First term --> [tex]a_1=9[/tex]
Common Difference --> [tex]d=8[/tex]
Substitute:
[tex]a_n=9+(n-1)(8)[/tex]
[tex]a_n=9+8(n-1)[/tex]
Determine whether a triangle with the given side lengths is a right triangle.
Answer:
See answer below.
Step-by-step explanation:
This is true for all right triangle a² + b² = c² were c = the largest number
9, 12, 15 A right triangle
21, 28, 35 A right triangle
9, 13, 16 Not a right triangle
10, 11, 15 Not a right triangle
(SAT Prep) Find the value of x
Answer:
x = 36
Step-by-step explanation:
3x+2x=180
5x=180
x=36
Answer:
x=36 degrees
Step-by-step explanation:
A shipping container will be used to transport several 60-kilogram crates across the country by rail. The greatest weight that can be loaded into the container is 26000 kilograms. Other shipments weighing 13200 kilograms have already been loaded into the container. What is the greatest number of 60-kilogram crates that can be loaded into the shipping container?
Answer:
213 crates
Step-by-step explanation:
There is enough space for 26000 kg - 13200 kg = 12800 kg. Divide this by 60 and you get 213 and 1/3. You cannot put 1/3 of a crate, so it is 213 crates.
Write an eighth-degree polynomial in factored form that is decreasing at both ends , has a single root at -2, a double root at 3 and 0 and triple root at -1
Answer:
Step-by-step explanation:
y = -1(x + 2)(x - 3)(x - 3)(x + 0)(x + 0)(x + 1)(x + 1)(x + 1)
The 8 degree polynomial for the given roots can be written as p(x) = x⁸ - x⁷- 12x⁶ - 4x⁵ + 30x⁴ + 51x³ + 18x².
What is factor theorem?The factor theorem states that for a polynomial p(x) if there exists a real number a such that p(a) = 0, then (x - a) is one of the factors of p(x).
The roots of the polynomial are given as follows,
Number of roots at -2 = 1
Number of roots at 3 = 2
Number of roots at 0 = 2
And, number of roots at -1 = 3.
Now, the polynomial can be written using factor theorem as,
p(x) = x²(x + 2)(x - 3)²(x + 1)³
= x²(x + 2)(x²- 6x + 9)(x³ + 3x² + 3x + 1)
= x⁸ - x⁷- 12x⁶ - 4x⁵ + 30x⁴ + 51x³ + 18x²
Hence, the polynomial for given roots can be written as p(x) = x⁸ - x⁷- 12x⁶ - 4x⁵ + 30x⁴ + 51x³ + 18x².
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what is -5.3125 in The real Number System?
Answer:
It'd be a rational number
Step-by-step explanation:
Real numbers are a set of numbers containing all of the rational numbers and all of the irrational numbers.
Types of numbers in the rational number "section" are decimals, whole, mixed, and fraction numbers whether they are negative or positive they are rational numbers.
Irrational numbers are numbers that cannot be expressed as the ratio of two integers. So they would be square root, pi and more.
Use the table. What is the total amount of electricity a computer, a television, and a heater use in 1 hour? Show your work.
Answer:
Step-by-step explanation:
21
4x + 5
E
חו
What is the value of x?
Answer:
don't know
Step-by-step explanation:
A desk drawer is shaped like a rectangular prism. The height of the drawer is 7 inches. The bottom of the drawer has an area of 210 square inches.
What is the volume of the desk drawer?
Enter your answer in the box.
Answer:
1470 inches cubed
Step-by-step explanation:
Vol=length × width × height
But ALSO,
length × width = Area,
So we find another Volume equation,
Vol = BaseArea × height
This is the information you are given in the question.
Vol = 210 × 7
Vol = 1470 inches cubed
Find the measure of angle m
For the following inequality, find a solution for the variable. Show all of your work and use complete sentences to explain the solving process that you used to find a solution for the inequality. Be sure to include at least two terms from the word bank
1/4 x \leq -3
Answer:
x<=-12
Step-by-step explanation:
1/4x<=-3
*Multiply both sides by 4
x<=-12
and it's solved :)
8. A company makes electronic components for TV's. 95% pass final inspection (and 5% fail and need to be fixed). 120 components are inspected in one day. (10 points) b.What is the variance of the number that pass inspection in one day
Using the binomial distribution, it is found that the variance of the number that pass inspection in one day is 5.7.
For each component, there are only two possible outcomes, either it passes inspection, or it does not. The probability of a component passing inspections is independent of any other component, hence, the binomial distribution is used to solve this question.
Binomial probability distribution
Probability of exactly x successes on n repeated trials, with p probability, and has variance given by:
[tex]V(X) = np(1 - p)[/tex]
In this problem:
95% pass final inspection, hence [tex]p = 0.95[/tex]120 components are inspected in one day, hence [tex]n = 120[/tex].The variance is given by:
[tex]V(X) = np(1 - p) = 120(0.95)(0.05) = 5.7[/tex]
The variance of the number that pass inspection in one day is 5.7.
To learn more about the binomial distribution, you can take a look at https://brainly.com/question/24863377