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3 years ago

What happens to the area of a circle when the radius is doubled? (1 point) it is doubled?

Mathematics

1 answer:

Alina [70]3 years ago

7 0

I think the circle would grow bigger into an oval.

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What's 1 plus 1. please help me

m_a_m_a [10]

Answer: 2

Step-by-step explanation:

3 0

3 years ago

Read 2 more answers

16 cm + B 11 cm 4 cm

yawa3891 [41]

Answer:

Step-by-step explanation:

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3 years ago

Let X and Y be discrete random variables. Let E[X] and var[X] be the expected value and variance, respectively, of a random vari

Ulleksa [173]

Answer:

(a) $E[X+Y]=E[X]+E[Y]$

(b) $Var(X+Y)=Var(X)+Var(Y)$

Step-by-step explanation:

Let X and Y be discrete random variables and E(X) and Var(X) are the Expected Values and Variance of X respectively.

(a)We want to show that E[X + Y ] = E[X] + E[Y ].

When we have two random variables instead of one, we consider their joint distribution function.

For a function f(X,Y) of discrete variables X and Y, we can define

$E[f(X,Y)]=\sum_{x,y}f(x,y)\cdot P(X=x, Y=y).$

Since f(X,Y)=X+Y

$E[X+Y]=\sum_{x,y}(x+y)P(X=x,Y=y)\\=\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y).$

Let us look at the first of these sums.

$\sum_{x,y}xP(X=x,Y=y)\\=\sum_{x}x\sum_{y}P(X=x,Y=y)\\\text{Taking Marginal distribution of x}\\=\sum_{x}xP(X=x)=E[X].$

Similarly,

$\sum_{x,y}yP(X=x,Y=y)\\=\sum_{y}y\sum_{x}P(X=x,Y=y)\\\text{Taking Marginal distribution of y}\\=\sum_{y}yP(Y=y)=E[Y].$

Combining these two gives the formula:

$\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y) =E(X)+E(Y)$

Therefore:

$E[X+Y]=E[X]+E[Y] \text{ as required.}$

(b)We want to show that if X and Y are independent random variables, then:

$Var(X+Y)=Var(X)+Var(Y)$

By definition of Variance, we have that:

$Var(X+Y)=E(X+Y-E[X+Y]^2)$

$=E[(X-\mu_X +Y- \mu_Y)^2]\\=E[(X-\mu_X)^2 +(Y- \mu_Y)^2+2(X-\mu_X)(Y- \mu_Y)]\\$Since we have shown that expectation is linear$\\=E(X-\mu_X)^2 +E(Y- \mu_Y)^2+2E(X-\mu_X)(Y- \mu_Y)]\\=E[(X-E(X)]^2 +E[Y- E(Y)]^2+2Cov (X,Y)$

Since X and Y are independent, Cov(X,Y)=0

$=Var(X)+Var(Y)$

Therefore as required:

$Var(X+Y)=Var(X)+Var(Y)$

7 0

2 years ago

25 POINTS!

bekas [8.4K]

Answer:

y-5=4(x+3)

Step-by-step explanation:

y-y1=m(x-x1)

y-5=4(x-(-3))

y-5=4(x+3)

6 0

3 years ago

a line with slope 3 passes through point (0,10). What is the y-coordinate of the point on the line with x-coordinate 2

skad [1K]

The y-coordinate is 16

<h3>Solution:</h3>

Given that a line with slope 3 passes through point (0, 10)

To find the y-coordinate of the point on the line with x-coordinate 2

Which means the point is (2, y)

Let us find the required y co-ordinate using slope formula

The slope of line is given as:

For a line containing points $(x_1 , y_1)$ and $(x_2 , y_2)$ is given as:

$\text {slope}=m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$

$\text {Here } x_{1}=0 ; y_{1}=10 ; x_{2}=2 ; y_{2}=y$

Given that slope "m" = 3

Substituting the values we get,

$\begin{array}{l}{3=\frac{y-10}{2-0}} \\\\ {3=\frac{y-10}{2}} \\\\ {6=y-10} \\\\ {y=10+6=16}\end{array}$

Thus the y-coordinate is 16

8 0

3 years ago