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maxonik [38]
3 years ago
5

1) x+30 = 40

Mathematics
1 answer:
soldier1979 [14.2K]3 years ago
4 0

1)x+30=40

x=40-30

Answer :x=10

2)30-20+2x=10

10+2x=10

2x=0

Answer: x=0

3)3x-10+13=-2x+28

3x+3=-2x+28

3x+2x+3=28

3x+2x=28-3

5x=28-3

5x=25

x=5

4)13x-23-45=-7x+12

13x-68=-7x+12

13x+7x-68=12

13x+7x=12+68

20x=12+68

20x=80

x=4

5)2(x+4)=10x+24

2x+8=10x+24

2x-10x+8=24

2x-10x=24-8

-8x=24-8

-8x=16

x=-2

6)3(x-5)=1-(2x-4)

3x-15=1-(2x-4)

3x-15=1-2x+4

3x-15=5-2x

3x+2x-15=5

3x+2x=5+15

5x=5+15

5x=20

x=4

7)5x-10=15

5x=15+10

5x=25

x=5

8)x+4=x+6

4=6

no solution

PLEASE MARK ME AS BRAINLIEST

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b) The expected value is

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Since X is the number of absent students on Monday, the expectation E[X] is the number of students you can expect to be absent on average on any given Monday. According to the distribution, you can expect around 3 students to be consistently absent.

c) The variance is

V[X]=E[(X-E[X])^2]=E[X^2]-E[X]^2

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E[X^2]=\displaystyle\sum_xx^2\,f(x)=11.58

So the variance is

V[X]=11.58-3.16^2\approx1.59

The standard deviation is the square root of the variance:

\sqrt{V[X]}\approx1.26

d) Since Y=7X+3 is a linear combination of X, computing the expectation and variance of Y is easy:

E[Y]=E[7X+3]=7E[X]+3=25.12

V[Y]=V[7X+3]=7^2V[X]\approx78.13

e) The covariance of X and Y is

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We have

XY=X(7X+3)=7X^2+3X

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E[XY]=E[7X^2+3X]=7E[X^2]+3E[X]=90.54

Then the covariance is

\mathrm{Cov}[X,Y]=90.54-3.16\cdot25.12\approx11.16

f) Dividing the covariance by the variance of X gives

\dfrac{\mathrm{Cov}[X,Y]}{V[X]}\approx\dfrac{11.16}{1.59}\approx0.9638

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