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3 years ago

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A cylinder of volume 10pi with a circular bottom and no top is constructed out of two different matierials. the cost of the bott

om is $4/m^2 and the cost of the sides is 3/m^2. find the dimensions of the box that minimizes total cost.

1 answer:

Elena L [17]3 years ago

6 0

Answer? i need help too

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Help please!!!!!!!!!

In-s [12.5K]

ANSWER

24

EXPLANATION

For a matrix A of order n×n, the cofactor $C_{ij}$ of element $a_{ij}$ is defined to be

$C_{ij} = (-1)^{i+j} M_{ij}$

$M_{ij}$ is the minor of element $a_{ij}$ equal to the determinant of the matrix we get by taking matrix A and deleting row i and column j.

Here, we have

$C_{11} = (-1)^{1+1} M_{11} = M_{11}$

M₁₁ is the determinant of the matrix that is matrix A with row 1 and column 1 removed. The bold entries are the row and the column we delete.

$\begin{aligned} A=\begin{bmatrix} \bf 1 & \bf -6 & \bf -4\\ \bf 7 & 0 & -3 \\ \bf -9 & 8 & -8 \end{bmatrix} \implies M_{11} &= \text{det}\left(\begin{bmatrix} 0&-3 \\ 8&-8 \end{bmatrix} \right) \end{aligned}$

Since the determinant of a 2×2 matrix is

$\det\left( \begin{bmatrix} a & b \\ c& d \end{bmatrix} \right) = ad-bc$

it follows that

$\begin{aligned} A=\begin{bmatrix} \bf 1 & \bf -6 & \bf -4\\ \bf 7 & 0 & -3 \\ \bf -9 & 8 & -8 \end{bmatrix} \implies M_{11} &= \text{det}\left(\begin{bmatrix} 0&-3 \\ 8&-8 \end{bmatrix} \right) \\ &= (0)(-8) - (-3)(8) \\ &= -(-24) \\ &= 24 \end{aligned}$

so $C_{11} = M_{11} = 24$

4 0

3 years ago

the wheel of a unicycle has a radius of 14 inches. About how many rotations will it take for the unicyle to tavel 440 inches

sdas [7]

31 rotations, hope i was a big help to you

4 0

3 years ago

Solve 2(a + 7) = 5a - 13

timurjin [86]

Answer:

a = 9

Step-by-step explanation:

2(a + 7) = 5a - 13

We want to bring a to one side, I will choose to bring it to the right

First, expand the bracket by multiplying 2 with a + 7

2a + 14 = 5a - 13

Bring the -13 to the left by adding 13 to both sides

2a + 14 + 13 = 5a - 13 + 13

Simplify

2a + 27 = 5a

Bring the 2a to the right by subtracting 2a from both sides

2a - 2a + 27 = 5a - 2a

Simplify

27 = 5a - 2a

27 = 3a

Bring the 3 to the left by dividing both sides by 3

27÷3 = a

Simplify

a = 9

4 0

3 years ago

Can someone help me plz need this done by tmrw

iren2701 [21]

Answer:

X= -2

Step-by-step explanation:

herp derp herp derp

5 0

3 years ago

Hello, can you help me with a probability question, please:)

sladkih [1.3K]

Ok what is it that u need

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3 years ago