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3 years ago

What is the function rule for (1,6) (2,24) and (3,54)?

1 answer:

7 0

First, find a pattern in the relationship between the two numbers in each set:

1*6 = 6, 1 + 5 = 6, 1^n*6 = 6

2*12 = 24, 2 + 22 = 24, 2^2*6, 2^3*3 = 24

3*18 = 54, 3 + 52 = 54, 3^2*6 = 54, 3^3*2 = 54

Sorting through the possible relationships reveals that in each case the first value in (x,y) relates to the second by the equation x^2*6 = y

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If X is a r.v. such that E(X^n)=n! Find the m.g.f. of X,Mx(t). Also find the ch.f. of X,and from this deduce the distribution of

astraxan [27]

$M_X(t)=\mathbb E(e^{Xt})$
$M_X(t)=\mathbb E\left(1+Xt+\dfrac{t^2}{2!}X^2+\dfrac{t^3}{3!}X^3+\cdots\right)$
$M_X(t)=\mathbb E(1)+t\mathbb E(X)+\dfrac{t^2}{2!}\mathbb E(X^2)+\dfrac{t^3}{3!}\mathbb E(X^3)+\cdots$
$M_X(t)=1+t+t^2+t^3+\cdots$
$M_X(t)=\displaystyle\sum_{k\ge0}t^k=\frac1{1-t}$

provided that $|t|$ .

Similarly,

$\varphi_X(t)=\mathbb E(e^{iXt})$
$\varphi_X(t)=1+it+(it)^2+(it)^3+\cdots$
$\varphi_X(t)=(1-t^2+t^4-t^6+\cdots)+it(1-t^2+t^4-t^6+\cdots)$
$\varphi_X(t)=(1+it)(1-t^2+t^4-t^6+\cdots)$
$\varphi_X(t)=\dfrac{1+it}{1+t^2}=\dfrac1{1-it}$

You can find the CDF/PDF using any of the various inversion formulas. One way would be to compute

$F_X(x)=\displaystyle\frac12+\frac1{2\pi}\int_0^\infty\frac{e^{itx}\varphi_X(-t)-e^{-itx}\varphi_X(t)}{it}\,\mathrm dt$

The integral can be rewritten as

$\displaystyle\int_0^\infty\frac{2i\sin(tx)-2it\cos(tx)}{it(1+t^2)}\,\mathrm dt$

so that

$F_X(x)=\displaystyle\frac12+\frac1{2\pi}\int_0^\infty\frac{\sin(tx)-t\cos(tx)}{t(1+t^2)}\,\mathrm dt$

There are lots of ways to compute this integral. For instance, you can take the Laplace transform with respect to $x$ , which gives

$\displaystyle\mathcal L_s\left\{\int_0^\infty\frac{\sin(tx)-t\cos(tx)}{t(1+t^2)}\,\mathrm dt\right\}=\int_0^\infty\frac{1-s}{(1+t^2)(s^2+t^2)}\,\mathrm dt$
$=\displaystyle\frac{\pi(1-s)}{2s(1+s)}$

and taking the inverse transform returns

$F_X(x)=\dfrac12+\dfrac1\pi\left(\dfrac\pi2-\pi e^{-x}\right)=1-e^{-x}$

which describes an exponential distribution with parameter $\lambda=1$ .

6 0

3 years ago

Which is more, 7,037 yards or 4 miles

balandron [24]

4 miles are about 7040 yards so they are very close but a mile is longer.

8 0

2 years ago

Please please please help fast this is a BIG deal

aniked [119]

Answer:

190.625 ft^2

Step-by-step explanation:

A = bh = (15.25) * (12.5) = 190.625 ft^2

5 0

2 years ago

Read 2 more answers

(NEED DONE SOON) The measure of two supplementary angles are 4x - 24 and 4(2x - 3). What is x

Zarrin [17]

Answer:

x = 12

Step-by-step explanation:

A pair of supplementary angles added together MUST equal 180. Therefore, as you are given two angles with the measures of (4x - 24) and 4(2x - 3), they must add together to equal 180. So, we get this equation:

(4x - 24) + 4(2x - 3) = 180

4x - 24 + 8x - 12 = 180 (we distributed 4(2x-3))

12x - 36 = 180

12x = 144

x = 12, -12

Therefore, x is 12 because -12 would mean that (4x-24) and 4(2x-3) are both negative, which is impossible for an angle measure.

5 0

2 years ago

What is the second term of (p+q)^5 1. 25p^4 2. 5p^4q 3. 25p^4q 4. 125p^4q

yaroslaw [1]

I hope this helps you