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Anastaziya [24]
3 years ago
12

Find the inverse of ????−7 −2

Mathematics
1 answer:
Masja [62]3 years ago
6 0

Answer:

A^{-1}=\begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}

Step-by-step explanation:

A=\begin{bmatrix}-7 & -2\\ 4 & 1\end{bmatrix}

det\ A=-7\times 1-(-2)\times 4\\\Rightarrow det\ A=1

A^{-1}=\frac{1}{det\ A}\begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}\\\Rightarrow A^{-1}=\frac{1}{1}\begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}\\\Rightarrow A^{-1}=\begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}

\therefore A^{-1}=\begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}

A.A^{-1}=\begin{bmatrix}-7 & -2\\ 4 & 1\end{bmatrix}\times \begin{bmatrix}1 & 2\\ -4 & -7\end{bmatrix}\\\Rightarrow A.A^{-1}=\begin{pmatrix}\left(-7\right)\cdot \:1+\left(-2\right)\left(-4\right)&\left(-7\right)\cdot \:2+\left(-2\right)\left(-7\right)\\ 4\cdot \:1+1\cdot \left(-4\right)&4\cdot \:2+1\cdot \left(-7\right)\end{pmatrix}\\\Rightarrow A.A^{-1}=\begin{pmatrix}1&0\\ 0&1\end{pmatrix}

Hence, confirmed

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Step-by-step explanation:

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Class 11

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Solve for x:sinx+sin2x+sin3x=cosx+cos2x+cos3x in the interval 0≤x≤2π.

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Solution

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Verified by Toppr

We write the given equation as

(sinx+sin3x)+sin2x=(cosx+cos3x)+cos2x

or 2sin2xcosx+sin2x=2cos2xcosx+cos2x

or sin2x(2cosx+1)=cos2x(2cosx+1)

or (sin2x−cos2x)(2cosx+1)=0

∴sin2x−cos2x=0 or 2cosx+1=0

If sin2x−cos2x=0, then tan2x=1,

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8

π

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If 2cosx+1=0, then cosx=−1/2 (2)

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x=π/8,5π/8,9π/8,13π/8. (n=0,1,2,3)

and (2) gives x=2π/3,4π/3. (for n=0,1)

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2 years ago
Jernel has to figure out the area of her square garage. she knows that one side of the garage is equal to the length of her rabb
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Step-by-step explanation:

Given: Jernel has to figure out the area of her square garage.

She knows that one side of the garage is equal to the length of her rabbit pen.

Now, the length of the rabbit pen = 10 units

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3 years ago
An ornithologist has 4 bird feeders at separate locations. She wonders if birds are equally likely to visit each of the feeders.
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Answer:

the x² test statistic 13.71

Option a) 13.71 is the correct answer.

Step-by-step explanation:

Given the data in the question;

Feeder                     1      2      3       4

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data sample = 300

Expected e_i = 300 / 4 = 75

the x² test statistic = ?

X^2_{stat = ∑[ (o_i - e_i)²/e_i]

X^2_{stat = [ (60 - 75)² / 75 ] + [ (90 - 75)² / 75 ] + [ (92 - 75)² / 75 ] + [ (58 - 75)² / 75 ]

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Therefore, the x² test statistic 13.71

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V = xxy = x^{2}y

We also know that the <span>bin is constructed from 48 square feet of sheet metal, s</span>o:

Surface area of the square base = x^{2}

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Therefore, the total area of the cube is:

A = 48 ft^{2} =  x^{2} + 4xy

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Substituting this value in V:

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Solving for x:

x =  \sqrt{\frac{48}{3}} =  \sqrt{16} = 4

Solving for y:

y =  \frac{48- 4^{2} }{(4)(4)} = 2

Then, <span>the dimensions of the largest volume of such a bin is:
</span>
Length = 4 ft
Width =  4 ft
Height = 2 ft

And its volume is:

V = (4^{2} )(2) = 32 ft^{3}

8 0
3 years ago
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