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2 years ago

What is the difference between explicit and recursive sequences ?

2 answers:

7 0

An explicit formula for a sequence allows you to find the value of any term in the sequence. A recursive formula for a sequence allows you to find the value of the nth term in the sequence if you know the value of the (n-1)th term in the sequence.

bulgar [2K]2 years ago

7 0

Answer:

An explicit formula for a sequence allows you to find the value of any term in the sequence. ... A recursive formula for a sequence allows you to find the value of the nth term in the sequence if you know the value of the (n-1)th term in the sequence.

Step-by-step explanation:

You might be interested in

Give the prime factorization of the number. use exponents when possible 126

nataly862011 [7]

Answer:

=2*3^2 *7

Step-by-step explanation:

Prime factorization means to simplify 126 down to prime numbers

126 = 2*63

= 2* 9*7

= 2*3*3*7

Since 2 3 and 7 are prime numbers, we rewrite these with exponents

=2*3^2 *7

3 0

3 years ago

Solve the following differential equation using using characteristic equation using Laplace Transform i. ii y" +y sin 2t, y(0) 2

kifflom [539]

Answer:

The solution of the differential equation is $y(t)= - \frac{1}{3} Sin(2t)+2 Cos(t)+\frac{5}{3} Sin(t)$

Step-by-step explanation:

The differential equation is given by: y" + y = Sin(2t)

i) Using characteristic equation:

The characteristic equation method assumes that y(t)= $e^{rt}$ , where "r" is a constant.

We find the solution of the homogeneus differential equation:

y" + y = 0

$y'=re^{rt}$

$y"=r^{2}e^{rt}$

$r^{2}e^{rt}+e^{rt}=0$

$(r^{2}+1)e^{rt}=0$

As $e^{rt}$ could never be zero, the term (r²+1) must be zero:

(r²+1)=0

r=±i

The solution of the homogeneus differential equation is:

$y(t)_{h}=c_{1}e^{it}+c_{2}e^{-it}$

Using Euler's formula:

$y(t)_{h}=c_{1}[Sin(t)+iCos(t)]+c_{2}[Sin(t)-iCos(t)]$

$y(t)_{h}=(c_{1}+c_{2})Sin(t)+(c_{1}-c_{2})iCos(t)$

$y(t)_{h}=C_{1}Sin(t)+C_{2}Cos(t)$

The particular solution of the differential equation is given by:

$y(t)_{p}=ASin(2t)+BCos(2t)$

$y'(t)_{p}=2ACos(2t)-2BSin(2t)$

$y''(t)_{p}=-4ASin(2t)-4BCos(2t)$

So we use these derivatives in the differential equation:

$-4ASin(2t)-4BCos(2t)+ASin(2t)+BCos(2t)=Sin(2t)$

$-3ASin(2t)-3BCos(2t)=Sin(2t)$

As there is not a term for Cos(2t), B is equal to 0.

So the value A=-1/3

The solution is the sum of the particular function and the homogeneous function:

$y(t)= - \frac{1}{3} Sin(2t) + C_{1} Sin(t) + C_{2} Cos(t)$

Using the initial conditions we can check that C1=5/3 and C2=2

ii) Using Laplace Transform:

To solve the differential equation we use the Laplace transformation in both members:

ℒ[y" + y]=ℒ[Sin(2t)]

ℒ[y"]+ℒ[y]=ℒ[Sin(2t)]

By using the Table of Laplace Transform we get:

ℒ[y"]=s²·ℒ[y]-s·y(0)-y'(0)=s²·Y(s) -2s-1

ℒ[y]=Y(s)

ℒ[Sin(2t)]= $\frac{2}{(s^{2}+4)}$

We replace the previous data in the equation:

s²·Y(s) -2s-1+Y(s) = $\frac{2}{(s^{2}+4)}$

(s²+1)·Y(s)-2s-1= $\frac{2}{(s^{2}+4)}$

(s²+1)·Y(s)= $\frac{2}{(s^{2}+4)}+2s+1=\frac{2+2s(s^{2}+4)+s^{2}+4}{(s^{2}+4)}$

Y(s)= $\frac{2+2s(s^{2}+4)+s^{2}+4}{(s^{2}+4)(s^{2}+1)}$

Y(s)= $\frac{2s^{3}+s^{2}+8s+6}{(s^{2}+4)(s^{2}+1)}$

Using partial franction method:

$\frac{2s^{3}+s^{2}+8s+6}{(s^{2}+4)(s^{2}+1)}=\frac{As+B}{s^{2}+4} +\frac{Cs+D}{s^{2}+1}$

2s^{3}+s^{2}+8s+6=(As+B)(s²+1)+(Cs+D)(s²+4)

2s^{3}+s^{2}+8s+6=s³(A+C)+s²(B+D)+s(A+4C)+(B+4D)

We solve the equation system:

A+C=2

B+D=1

A+4C=8

B+4D=6

The solutions are:

A=0 ; B= -2/3 ; C=2 ; D=5/3

So,

Y(s)= $\frac{-\frac{2}{3} }{s^{2}+4} +\frac{2s+\frac{5}{3} }{s^{2}+1}$

Y(s)= $-\frac{1}{3} \frac{2}{s^{2}+4} +2\frac{s }{s^{2}+1}+\frac{5}{3}\frac{1}{s^{2}+1}$

By using the inverse of the Laplace transform:

ℒ⁻¹[Y(s)]=ℒ⁻¹[ $-\frac{1}{3} \frac{2}{s^{2}+4}$ ]-ℒ⁻¹[ $2\frac{s }{s^{2}+1}$ ]+ℒ⁻¹[ $\frac{5}{3}\frac{1}{s^{2}+1}$ ]

$y(t)= - \frac{1}{3} Sin(2t)+2 Cos(t)+\frac{5}{3} Sin(t)$

3 0

3 years ago

Abby is registering at a Web site and must select a six-character password.The password can contain either letters or digits.

zaharov [31]

Answer:

a. 2176782336 with repeated characters. 1402410240 with no repeated characters.

b. 7964171460 when all letters can be repeated, but not numbers. 118813760 when only one number and letters can be repeated.

I believe that the password with all letters able to repeat and numbers not being able to is the most secure password, because if someone were to guess the password there is a 1/7964171460 chance of guessing the password.

Step-by-step explanation:

A. Since there are 26 different letters and 10 different numbers, there are 36 characters we can type. If characters can be repeated then, there is 2176782336 different passwords, since on all six number there are 36 possibilities each. So, 36 x 36 x 36 x 36 x 36 x 36 or 36^6 is to evaluated to find the answer. If characters are not to be repeated, there are 1402410240 different passwords, since on the first number there are 36, second has 35, third has 34, fourth has 33, fifth has 32, and sixth has 31. So, 36 x 35 x 34 x 33 x 32 x 31 is to be evaluated to solve this.

B. Since all characters that are letters can be repeated, then there are 26 letters to use forever and 10 numbers you can use with a limit. So, 36 x 35 x 34 x 33 x 32 x 31 which is to be solved if only numbers were to be used, which is 1402410240. Then, you add that with 36 x 35^5 and 36 x 35 x 34^4 and 36 x 35 x 34 x 33^3 and 36 x 35 x 34 x 33 x 32^2. which will be 7964171460. If the password must contain one digit, then you must multiply 10 with 26^5. Since, there is 10 different digits to use for the first number and 26 letters to choose from for the other five. So, it will be 26^5 times 10 which is 118813760.

6 0

3 years ago

What are the side lengths of a rectangle that has 8 square units and a perimeter of 12 units

telo118 [61]

The longest two sides will be 4 each and the shortest two sides will be 2 each

3 0

3 years ago

Let A = -4k+ 3 and B = 3k +17. If A = B, then what is the value of k?

kupik [55]

Answer:

k=-2

Step-by-step explanation:

Using substitution to find what you're missing, (in this case k) is when you plug each letter into the other equation:

-4k+3=3k+17

So now solve for k:

subtract 3 from both sides...

-4k=3k+14

subtract 3k from both sides to combine with -4k...

-7k=14

divide -7 from both sides...

k=-2

3 0

2 years ago