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3 years ago

Does anyone know how to do this?

Mathematics

1 answer:

kolezko [41]3 years ago

3 0

Answer:

x = 1
y = -7

Step-by-step explanation:

The coefficients of x and y do not have any "nice" relations, so doing this by elimination is just "brute force" with no particular subtlety.

After multiplying by appropriate numbers, you want the coefficient of one of the variables in one equation to be the opposite of the coefficient of the same variable in the other equation. Here, we can get that by multiplying the first equation by 7 and the second equation by 2.

7(2x +3y = -19) ⇒ 14x +21y = -133

2(-7x +2y = -21) ⇒ -14x +4y = -42

Adding these equations with opposite x-coefficients eliminates the x-terms. (That is how the "elimination" method gets its name.)

(14x +21y) +(-14x +4y) = (-133) +(-42)

25y = -175 . . . . . . . . simplify

y = -7 . . . . . . . . . . . divide by 25

Substituting this value into the first equation gives ...

2x +3(-7) = -19

2x = 2 . . . . . . . . . add 21

x = 1 . . . . . . . . . divide by 2

The solution is x = 1, y = -7.

_____

<em>Additional comment</em>

The multipliers used in this process are essentially the coefficients of one of the variables, with one of them negated. Here, we chose the x-coefficients, because negating one of them gives two positive multipliers. We judge it easier to do the arithmetic using positive numbers.

Had we chosen to use the y-coefficients (3 and 2) for our multipliers, we would probably multiply the first equation by 2, and the second equation by -3. That way, the remaining x-coefficient would be positive.

Planning ahead is helpful, but not essential. It can help to avoid errors and make the work easier to do.

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If 2x+5= 12 for some value of x, then what does 6x+20 equal???

ANEK [815]

1. Solve for x in 2x + 5 = 12
2x + 5 = 12 Subtract 5 from both sides.
2x = 7 Divide 2 from both sides.
x = 3.5

2. Substitute 3.5 in for x in 6x + 20
6(3.5) + 20
21 + 20
41

Your answer is 41.

6 0

3 years ago

Read 2 more answers

The standard deviation of a sample taken from population A is 17.6 for a sample of 25.

lawyer [7]

Answer:

The standard deviation of the sample mean differences is _5.23_

Step-by-step explanation:

We have a sample of a population A and a sample of a population B.

For the sample of population A, the standard deviation $\sigma_A$ is

$\sigma_A = 17.6$

The sample size $n_A$ is:

$n_A = 25$ .

For the sample of population B, the standard deviation $\sigma_B$ is

$\sigma_B = 21.2$

The sample size $n_B$ is:

$n_B = 30$ .

Then the standard deviation for the difference of means has the following form:

$\sigma=\sqrt{\frac{\sigma_A^2}{n_A}+\frac{\sigma_B^2}{n_B}}$

Finally

$\sigma=\sqrt{\frac{17.6^2}{25}+\frac{21.2^2}{30}}\\\\\sigma= 5.23$

7 0

3 years ago

Julio bought a total of 20 medium and large pumpkins. If he spent $53 and bought 6 more large pumpkins as medium pumpkins, how m

Tatiana [17]

20 medium and large pumpkins

m ... number of medium pumpkins
l ... number of large pumpkins

20 = m + l
20 = m + (m + 6)
20 = 2 * m + 6
2 * m = 20 - 6
2 * m = 14
m = 7 medium pumpkins

l = 20 - 7 = 13 large pumpkins

Result: Julio bought 13 large pumpkins.

5 0

3 years ago

You are designing a miniature golf course and need to calculate the surface area and volume of many of the objects that will be

laiz [17]

a. To solve the first part, we are going to use the formula for the surface area of a sphere: $A=4 \pi r^2$
where
$A$ is the surface area of the sphere
$r$ is the radius of the sphere
We know from our problem that $r=5ft$ ; so lets replace that value in our formula:
$A=4 \pi (5ft)^2$
$A=314.16ft^2$

To solve the second part, we are going to use the formula for the volume of a sphere: $V= \frac{4}{3} \pi r^3$
Where
$V$ is the volume of the sphere
$r$ is the radius
We know form our problem that $r=5ft$ , so lets replace that in our formula:
$V= \frac{4}{3} \pi (5ft)^3$
$V=523.6ft^3$

We can conclude that the surface area of the sphere is 314.16 square feet and its volume is 523.6 cubic feet.

b. To solve the first part, we are going to use the formula for the surface area of a square pyramid: $A=a^2+2a \sqrt{ \frac{a^2}{4} +h^2}$
where
$A$ is the surface area
$a$ is the measure of the base
$h$ is the height of the pyramid
We know form our problem that $a=8ft$ and $h=12ft$ , so lets replace those value sin our formula:
$A=(8ft)^2+2(8ft) \sqrt{ \frac{(8ft)^2}{4} +(12ft)^2}$
$A=266.39ft^2$

To solve the second part, we are going to use the formula for the volume of a square pyramid: $V=a^2 \frac{h}{3}$
where
$V$ is the volume
$a$ is the measure of the base
$h$ is the height of the pyramid
We know form our problem that $a=8ft$ and $h=12ft$ , so lets replace those value sin our formula:
$V=(8ft)^2 \frac{(12ft)}{3}$
$V=256ft^3$

We can conclude that the surface area of our pyramid is 266.39 square feet and its volume is 256 cubic feet.

c. To solve the first part, we are going to use the formula for the surface area of a circular cone: $A= \pi r(r+ \sqrt{h^2+r^2}$
where
$A$ is the surface area
$r$ is the radius of the circular base
$h$ is the height of the cone
We know form our problem that $r=5ft$ and $h=8ft$ , so lets replace those values in our formula:
$A= \pi (5ft)[(5ft)+ \sqrt{(8ft)^2+(5ft)^2}]$
$A=226.73ft^2$

To solve the second part, we are going to use the formula for the volume os a circular cone: $V= \pi r^2 \frac{h}{3}$
where
$V$ is the volume
$r$ is the radius of the circular base
$h$ is the height of the cone
We know form our problem that $r=5ft$ and $h=8ft$ , so lets replace those values in our formula:
$V= \pi (5ft)^2 \frac{(8ft)}{3}$
$V=209.44ft^3$

We can conclude that the surface area of our cone is 226.73 square feet and its surface area is 209.44 cubic feet.

d. To solve the first part, we are going to use the formula for the surface area of a rectangular prism: $A=2(wl+hl+hw)$
where
$A$ is the surface area
$w$ is the width
$l$ is the length
$h$ is the height
We know from our problem that $w=6ft$ , $l=10ft$ , and $h=16ft$ , so lets replace those values in our formula:
$A=2[(6ft)(10ft)+(16ft)(10ft)+(16ft)(6ft)]$
$A=632ft^2$

To solve the second part, we are going to use the formula for the volume of a rectangular prism: $V=whl$
where
$V$ is the volume
$w$ is the width
$l$ is the length
$h$ is the height
We know from our problem that $w=6ft$ , $l=10ft$ , and $h=16ft$ , so lets replace those values in our formula:
$V=(6ft)(16ft)(10ft)$
$V=960ft^3$

We can conclude that the surface area of our solid is 632 square feet and its volume is 960 cubic feet.

e. Remember that a face of a polygon is a side of polygon.
- A sphere has no faces.
- A square pyramid has 5 faces.
- A cone has 1 face.
- A rectangular prism has 6 faces.
Total faces: 5 + 1 + 6 = 12 faces

<span>We can conclude that there are 12 faces in on the four geometric shapes on the holes.
</span>
f. Remember that an edge is a line segment on the boundary of the polygon.
- A sphere has no edges.
- A cone has no edges.
- A rectangular pyramid has 8 edges.
- A rectangular prism has 12 edges.
Total edges: 8 + 20 = 20 edges

Since we have 20 edges in total, we can conclude that your boss will need 20 brackets on the four shapes.

g. Remember that the vertices are the corner points of a polygon.
- A sphere has no vertices.
- A cone has no vertices.
- A rectangular pyramid has 5 vertices.
- A rectangular prism has 8 vertices.
Total vertices: 5 + 8 = 13 vertices

We can conclude that there are 0 vertices for the sphere and the cone; there are 5 vertices for the pyramid, and there are are 8 vertices for the solid (rectangular prism). We can also conclude that your boss will need 13 brackets for the vertices of the four figures.

7 0

3 years ago

Suppose a camping tent has a center pole that is 6 feet high. If the sides of the tent make 40° angles with the ground, how wide

Montano1993 [528]

Answer:

14.3 feet

Step-by-step explanation:

See attached photo for work...

8 0

3 years ago