Exercise 7.6.5

We see immediately that A = 2, thus B = 0. Since B = 0, D = -1. Since A = 2 and B = 0, then C = 1. So the decomposition is

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Exercise 7.6.4

Use Heavyside's method to find A:

Therefore

Clearing the fractions yields

So B = 1 and C = 3. So the decomposition is

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Exercise 7.6.3

We can find A and C, but not B, by Heavyside's Method:

Thus

Clearing the fractions by multiplying both sides by the least common denominator yields:

Thus, B = 2. So the decomposition is

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Exercise 7.6.2

We can find B, but not A, using Heavyside's Method:

Thus,

Next, we multiply through by the least common denominator to clear the fractions:

So A = 1. The decomposition is

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Exercise 7.6.1

Using Heavyside's Method:

So the partial fraction decomposition is

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Exercise 7.5.4
 
 

2 x - 5 y + 2 z =  0
  x + 3 y +   z = -1
        y - 3 z =  0

Using Cramer's Rule

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Exercise 7.5.3
 

  5 x + 3 y = - 2
 -3 x +   y =   4

Using Cramer's Rule

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Exercise 7.5.2

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Exercise 7.5.1

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Exercise 7.4.1
 

S1
|  x  +    y + z  =   0
|- x  +  2 y      =  -1
|  x         + z  =   1>
The corresponding matrix is:>

   1   1   1   0
  -1   2   0  -1  E2 -->  E1 + E2 
   1   0   1   1  E3 --> -E1 + E3 

   1   1   1   0
   0   3   1  -1
   0  -1   0   1  E2 <--> E3>

   1   1   1   0
   0  -1   0   1  E2 --> -E2
   0   3   1  -1 

   1   1   1   0
   0   1   0  -1
   0   3   1  -1  E3 --> -3E2 + E3

   1   1   1   0  Since this is triangularized, we begin the back substitution:
   0   1   0  -1
   0   0   1   2  E1 --> -E3 + E1

   1   1   0  -2
   0   1   0  -1
   0   0   1   2  E1 --> -E2 + E1

   1   0   0  -1
   0   1   0  -1
   0   0   1   2  Which corresponds to a solution

   x         = -1
       y     = -1
           z =  2
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Exercise 7.3.2
 

S1
| x  - y + z = 1
| x      + z = 1   E2 --> -E1 + E2
| x  + y + z = 2   E3 --> -E1 + E3

S2
|    x  - y + z = 1
|         y     = 0
|        2y     = 1   E3 --> -2E2 + E3

S3
|    x  - y + z = 1
|         y     = 0
|             0 = 1  Thus the system is inconsistent.
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Exercise 7.3.1
 

S1
| x + 2 y  + z = 0
|       y  - z = 2
Insert a third equation to represent all possible values of z.
 
S2
| x + 2 y  + z =  0      E1 --> -E3 + E1
|       y  - z =  2      E2 -->  E3 + E2
|               z =  t

S3
| x + 2 y      = -t      E1 --> -2E2 + E1
|          y      =  2 - t
|               z =  t  

S4
|    x            = -4 + t
|          y      =  2 - t
|               z =  t
which is the 'solution'. There are actually an infinite number of solutions, one for each value of t. The system is dependent.

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Exercise 7.2.4
 

S1
| x + 2y  -  z =  1
| x       +  z =  3   E2 --> -E1 + E2
|      y  +  z =  1

S2
| x + 2y  -  z =  1
|      - 2y  + 2z =  2   E2 <--> E3
|      y  +  z =  1

S3
| x + 2y  -  z =  1
|      y  +  z =  1
|      - 2y  + 2z =  2   E3 --> 2E2 + E3

S4
| x + 2y  -  z =  1
|      y  -  z = -1
|              4z =  4  E3 --> (1/4)E3

S5
| x + 2y  -  z =  1
|      y  -  z = -1
|               z =  1
Solving for y by back-substitution, y = 0. Using the values of z and y, we solve the first equation for x, getting x = 2.

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Exercise 7.2.3
 

S1
| x + 2 y  -   z =  0
|   - 3 y  + 3 z =  0  E2 --> -(1/3)E2
|     7 y  -   z = -6

S2
| x + 2 y  -   z =  0
|       y  -   z =  0
|     7 y  -   z = -6  E3 --> -7E2 + E3

S3
| x + 2 y  -   z =  0
|       y  -   z =  0
|            6 z = -6
Solving the last equation, z = -1. Substitution into the second equation, y = -1. Substituting these two values into the first equation yields x = 1.

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Exercise 7.2.2
 

S1
|     x + 2 y  -   z =   0
|   2 x +   y  +   z =   0  E2--> - 2 E1 + E2
| - 3 x +   y  + 2 z = - 6  E3-->   3 E1 + E3

S2
|     x + 2 y  -   z =   0
|       - 3 y  + 3 z =   0
|         7 y  -   z = - 6
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Exercise 7.2.1
 

S1
| x + 2 y - z = 3
|       y - z = 1
|           z = 2
Substituting z = 2 into the second equation gives y - 2 = 1, so y = 3. Substituting these two values into equation 1 yields x + 6 - 2 = 3, so x = -1.

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Exercise 7.1.2
 

S1
| x + y =  1
|2x + y = -1
Solving the first equation for y in terms of x yields y = 1 - x.

Substituting y = 1 - x into the second equation and simplifying yields x +1 = -1. So x = -2. Since
y = 1 - x, then y = 3.

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Exercise 7.1.1
 

S1
| x + y  = 0
| x + y2 = 0
Solving the first equation for y in terms of x yields y = - x. Substituting into the second equation and simplifying yields x + x2 = 0. Factoring the expression on the left yields

x ( 1 + x ) = 0

So, either x = 0 and y = 0, or x = -1 and y = 1.

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