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Soloha48 [4]
3 years ago
13

Select the correct answer from each drop-down menu. A system of equations and its solution are given system A x-y=7 -3x+9y=-39 s

olution: (4,-3) complete the sentences to explain what steps were followed to obtain the system of equations below. system B x-y=7 6y=-18
Mathematics
1 answer:
galina1969 [7]3 years ago
4 0

Answer:

Step-by-step explanation:

x-y=7

-3x+9y=-39

Divide the second equation by 3

-x +3y = -13

Add this to the first equation

x-y=7

-x +3y = -13

----------------------

0x +2y = -6

Divide by 2

2y/2 = -6/2

y = -3

Now find x

x-y = 7

x -(-3) = 7

x+3 = 7

Subtract 3 from each side

x = 4

(4,-3)

Or by substitution

x-y=7  

solve for x

x = 7+y

-3x+9y=-39

Substitute y+7 in for x

-3(7+y) +9y = -39

Distribute

-21 -3y +9y = -39

Combine like terms

-21 +6y = -39

Add 21 to each side

6y = -18

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Answer:

i don't know j dhf jfjyk jrkr htjt jrkr dr rkr

5 0
2 years ago
the length of a sandbox is three feet longer than it’s width. Write the expression that would represent the area of the sandbox.
Rashid [163]

Part A : D.)

Part B : Length of the sandbox is 10 feet.

Step-by-step explanation:

Given,

Perimeter = 29 ft

We need to find the equation for the perimeter and also the length of the sandbox.

Solution,

Let the width of the sandbox be 'w'.

Now as per question said;

The length of the sandbox is 1 foot longer than twice the width of the sandbox.

So we can say that;

Length =

Now we know that the perimeter is equal to the sum of twice of length and width.

framing in equation form, we get;

Perimeter =

we have given the perimeter, so on substituting the value, we get;

Hence The equation used to find the width is  .

Now we solve for 'w'.

Applying distributive property, we get;

Subtracting both side by '2' we get

Dividing both side by 6 we get;

Width of the sandbox = 4.5 ft

Length of the sandbox =

Hence Length of the sandbox is 10 feet.

6 0
3 years ago
A zoologist is studying four very closely related feline species. She wishes to compare their gestation periods. An observationa
diamong [38]

Answer:

p_v= 0.01

Since the significance level is 0.05 we see that pv so we have enough evidence to reject the null hypothesis. And the best conclusion for this case would be:

b. at least some, but not all, of the gestation periods across all four species are the same

Because is only to identify if AT LEAST one mean is different, NOT to conclude that the all the means are different.

Step-by-step explanation:

Previous concepts

Analysis of variance (ANOVA) "is used to analyze the differences among group means in a sample".  

The sum of squares "is the sum of the square of variation, where variation is defined as the spread between each individual value and the grand mean"  

Solution to the problem

The hypothesis for this case are:

Null hypothesis: \mu_{A}=\mu_{B}=\mu_{C}= \mu_D

Alternative hypothesis: Not all the means are equal \mu_{i}\neq \mu_{j}, i,j=A,B,C,D

In order to find the mean square between treatments (MSTR), we need to find first the sum of squares and the degrees of freedom.

If we assume that we have p=4 groups and on each group from j=1,\dots,p we have n_j individuals on each group we can define the following formulas of variation:  

SS_{total}=\sum_{j=1}^p \sum_{i=1}^{n_j} (x_{ij}-\bar x)^2  

SS_{between}=SS_{model}=\sum_{j=1}^p n_j (\bar x_{j}-\bar x)^2  

SS_{within}=SS_{error}=\sum_{j=1}^p \sum_{i=1}^{n_j} (x_{ij}-\bar x_j)^2  

And we have this property  

SST=SS_{between}+SS_{within}  

And in order to test this hypothesis we need to ue an F statistic and for this case the p value calculated is

p_v= 0.01

Since the significance level is 0.05 we see that pv so we have enough evidence to reject the null hypothesis. And the best conclusion for this case would be:

b. at least some, but not all, of the gestation periods across all four species are the same

Because is only to identify if AT LEAST one mean is different NOT to conclude that the all the means are different.

8 0
4 years ago
Jasmine is making cookies for everyone in her class and she wants to make sure everyone gets at least one cookie. The recipe cal
andreev551 [17]

Answer:

1.5 or 3/2 teaspoons

Step-by-step explanation:

If her class has 36 students, and there are 12 cookies in every batch, then she needs 3 batches to give everyone in her class 1 cookie each. It takes 1/2 teaspoon for every recipe, so she needs 3 of those. 3 × 1/2 = 1.5 (or 3/2)

7 0
3 years ago
the mean average distance that jack runs in his last 10 runs is 5.7 miles. work out the distance that he would need to make this
ziro4ka [17]

Answer:

9 miles

Step-by-step explanation:

mean is calculated as

mean = \frac{sum}{count} , then

\frac{sum}{10} = 5.7 ( multiply both sides by 10 )

sum = 57

let x be the distance he needs to cover so mean is 6 , that is

\frac{sum+x}{11} = 6 ( multiply both sides by 11 )

sum + x = 66 , that is

57 + x = 66 ( subtract 57 from both sides )

x = 9

That is he would have to run 9 miles

3 0
2 years ago
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