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3 years ago

Determine whether y varies directly with x. If so, find the constant of variation k. 7y = –x

Mathematics

2 answers:

saul85 [17]3 years ago

8 0

Answer: B

Explanation: comment above me LOL

fomenos3 years ago

3 0

Answer:

Step-by-step explanation:

The equation of quantities in direct variation is

y = kx ← k is the constant of variation

Given

7y = - x ( divide both sides by 7 )

y = - $\frac{1}{7}$ x ← in direct variation form

with k = - $\frac{1}{7}$

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HELP FAST BUT BE CORRECT(:

Marrrta [24]

the correct answer is C.

3 0

2 years ago

Solve for XX. Assume XX is a 2×22×2 matrix and II denotes the 2×22×2 identity matrix. Do not use decimal numbers in your answer.

sveticcg [70]

The question is incomplete. The complete question is as follows:

Solve for X. Assume X is a 2x2 matrix and I denotes the 2x2 identity matrix. Do not use decimal numbers in your answer. If there are fractions, leave them unevaluated.

$\left[\begin{array}{cc}2&8\\-6&-9\end{array}\right]$ · X· $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ =I.

First, we have to identify the matrix I. As it was said, the matrix is the identiy matrix, which means

I = $\left[\begin{array}{ccc}1&0\\0&1\end{array}\right]$

So, $\left[\begin{array}{cc}2&8\\-6&-9\end{array}\right]$ · X· $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ = $\left[\begin{array}{ccc}1&0\\0&1\end{array}\right]$

Isolating the X, we have

X· $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ = $\left[\begin{array}{cc}2&8\\-6&-9\end{array}\right]$ - $\left[\begin{array}{ccc}1&0\\0&1\end{array}\right]$

Resolving:

X· $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ = $\left[\begin{array}{ccc}2-1&8-0\\-6-0&-9-1\end{array}\right]$

X· $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ = $\left[\begin{array}{ccc}1&8\\-6&-10\end{array}\right]$

Now, we have a problem similar to A.X=B. To solve it and because we don't divide matrices, we do X=A⁻¹·B. In this case,

X= $\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ ⁻¹· $\left[\begin{array}{ccc}1&8\\-6&-10\end{array}\right]$

Now, a matrix with index -1 is called Inverse Matrix and is calculated as: A . A⁻¹ = I.

So,

$\left[\begin{array}{ccc}9&-3\\7&-6\end{array}\right]$ · $\left[\begin{array}{ccc}a&b\\c&d\end{array}\right]$ = $\left[\begin{array}{ccc}1&0\\0&1\end{array}\right]$

9a - 3b = 1

7a - 6b = 0

9c - 3d = 0

7c - 6d = 1

Resolving these equations, we have a= $\frac{2}{11}$ ; b= $\frac{7}{33}$ ; c= $\frac{-1}{11}$ and d= $\frac{-3}{11}$ . Substituting:

X= $\left[\begin{array}{ccc}\frac{2}{11} &\frac{-1}{11} \\\frac{7}{33}&\frac{-3}{11} \end{array}\right]$ · $\left[\begin{array}{ccc}1&8\\-6&-10\end{array}\right]$

Multiplying the matrices, we have

X= $\left[\begin{array}{ccc}\frac{8}{11} &\frac{26}{11} \\\frac{39}{11}&\frac{198}{11} \end{array}\right]$

6 0

3 years ago

What is the height, in centimeters, of a rectangular prism that is 80 centimeters wide, 40 centimeters long, and has a volume of

Rainbow [258]

Answer:

The answer to your question is the letter E. 50

Step-by-step explanation:

Data

height = ?

Width = 80 cm

Length = 40 cm

Volume = 160000 cm³

Formula

Volume of a rectangular prism = Width x length x height

Substitution

160000 = 80 x 40 x height

Solve for height

height = 160000 / 80 x 40

Simplification

height = 160000/ 3200

Result

height = 50 cm

4 0

2 years ago

Find the probability of having 2,3, or 4 successes in five trials of a binomial experiment in which the probability of success i

Georgia [21]

Answer:

65.3%

Step-by-step explanation:

Binomial distribution PMF below (along with a description)

the probabilty of getting 2, 3, or 4 successes in 5 trials is just

p(2)+p(3)+p(4)

p(2)= 5C2*.4²*(1-.4)³ = .3456

p(3)= 5C3*.4³*(1-.4)²= .2304

p(4)= 5C4*.4⁴*(1-.4)=.0768

.3456+.2304+.0768= .6528

6 0

2 years ago

A gym membership is $100 sign-up fee and charges $20 a month thereafter. How much is the membership fee in a month?

trapecia [35]

Answer:

$120

Step-by-step explanation:

y = mx + b

The $100 sign up fee is a set amount, or the b value.

The $20 would be the m value since it the constant change, or the slope.

Thus, the equation would be y=20x + 100

The membership fee for 1 month would be --->

y= 20(1) +100

y= 20 + 100

y= $120

4 0

2 years ago