Answer:
- <u>Question 1:</u>
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- <u>Question 2:</u>
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- <u>Question 3:</u>
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- <u>Question 4:</u>
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Explanation:
<u>Question 1: Write down the differential equation the mass of the bacteria, m, satisfies: m′= .2m</u>
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a) By definition: ![m'=dm/dt](https://tex.z-dn.net/?f=m%27%3Ddm%2Fdt)
b) Given: ![rate=0.2m](https://tex.z-dn.net/?f=rate%3D0.2m)
c) By substitution: ![dm/dt=0.2m](https://tex.z-dn.net/?f=dm%2Fdt%3D0.2m)
<u>Question 2: Find the general solution of this equation. Use A as a constant of integration.</u>
a) <u>Separate variables</u>
![dm/m=0.2dt](https://tex.z-dn.net/?f=dm%2Fm%3D0.2dt)
b)<u> Integrate</u>
![\int dm/m=\int 0.2dt](https://tex.z-dn.net/?f=%5Cint%20dm%2Fm%3D%5Cint%200.2dt)
![ln(m)=0.2t+C](https://tex.z-dn.net/?f=ln%28m%29%3D0.2t%2BC)
c) <u>Antilogarithm</u>
![m=e^{0.2t+C}](https://tex.z-dn.net/?f=m%3De%5E%7B0.2t%2BC%7D)
![m=e^{0.2t}\cdot e^C](https://tex.z-dn.net/?f=m%3De%5E%7B0.2t%7D%5Ccdot%20e%5EC)
![e^C=A\\\\m=Ae^{(0.2t)}](https://tex.z-dn.net/?f=e%5EC%3DA%5C%5C%5C%5Cm%3DAe%5E%7B%280.2t%29%7D)
<u>Question 3. Which particular solution matches the additional information?</u>
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Use the measured rate of 4 grams per hour after 3 hours
![t=3hours,dm/dt=4g/h](https://tex.z-dn.net/?f=t%3D3hours%2Cdm%2Fdt%3D4g%2Fh)
First, find the mass at t = 3 hours
![dm/dt=0.2m\\\\4=0.2m\\\\m=4/0.2\\\\m=20g](https://tex.z-dn.net/?f=dm%2Fdt%3D0.2m%5C%5C%5C%5C4%3D0.2m%5C%5C%5C%5Cm%3D4%2F0.2%5C%5C%5C%5Cm%3D20g)
Now substitute in the general solution of the differential equation, to find A:
![m=Ae^{(0.2t)}\\\\20=Ae^{(0.2\times 3)}\\\\A=20/e^{(0.6)}\\\\A=10.976](https://tex.z-dn.net/?f=m%3DAe%5E%7B%280.2t%29%7D%5C%5C%5C%5C20%3DAe%5E%7B%280.2%5Ctimes%203%29%7D%5C%5C%5C%5CA%3D20%2Fe%5E%7B%280.6%29%7D%5C%5C%5C%5CA%3D10.976)
Round A to 1 significant figure:
<u>Particular solution:</u>
![m=10e^{(0.2t)}](https://tex.z-dn.net/?f=m%3D10e%5E%7B%280.2t%29%7D)
<u>Question 4. What was the mass of the bacteria at time =0?</u>
Substitute t = 0 in the equation of the particular solution:
![m=10e^{0}\\\\m=10g](https://tex.z-dn.net/?f=m%3D10e%5E%7B0%7D%5C%5C%5C%5Cm%3D10g)
So I believe you will have to do 10% x 7 as it has been seven years which will be 70% and 70% of 8000 is 5600 so the answer will be £5600
Graph B is the correct answer
The answer is not defined.
Explanation:
The given matrix is ![$\left[\begin{array}{cc}{2} & {4} \\ {1} & {-6}\end{array}\right]+\left[\begin{array}{c}{1} \\ {0}\end{array}\right]$](https://tex.z-dn.net/?f=%24%5Cleft%5B%5Cbegin%7Barray%7D%7Bcc%7D%7B2%7D%20%26%20%7B4%7D%20%5C%5C%20%7B1%7D%20%26%20%7B-6%7D%5Cend%7Barray%7D%5Cright%5D%2B%5Cleft%5B%5Cbegin%7Barray%7D%7Bc%7D%7B1%7D%20%5C%5C%20%7B0%7D%5Cend%7Barray%7D%5Cright%5D%24)
The matrix
has dimensions ![2\times 2](https://tex.z-dn.net/?f=2%5Ctimes%202)
This means that the matrix has 2 rows and 2 columns.
Also, the matrix
has dimensions ![2\times1](https://tex.z-dn.net/?f=2%5Ctimes1)
This means that the matrix has 2 rows and 1 column.
Since, the matrices can be added only if they have the same dimensions.
In other words, to add the matrices, the two matrices must have the same number of rows and same number of columns.
Since, the dimensions of the two matrices are not equal, the addition of these two matrices is not possible.
Hence, the addition of these two matrices is not defined.