Simultaneous Linear Equations/Examples

From ProofWiki
Jump to navigation Jump to search

Examples of Simultaneous Linear Equations

Arbitrary System $1$

The system of simultaneous linear equations:

\(\text {(1)}: \quad\) \(\ds x_1 - 2 x_2 + x_3\) \(=\) \(\ds 1\)
\(\text {(2)}: \quad\) \(\ds 2 x_1 - x_2 + x_3\) \(=\) \(\ds 2\)
\(\text {(3)}: \quad\) \(\ds 4 x_1 + x_2 - x_3\) \(=\) \(\ds 1\)

has as its solution set:

\(\ds x_1\) \(=\) \(\ds -\dfrac 1 2\)
\(\ds x_2\) \(=\) \(\ds \dfrac 1 2\)
\(\ds x_3\) \(=\) \(\ds \dfrac 3 2\)


Arbitrary System $2$

The system of simultaneous linear equations:

\(\text {(1)}: \quad\) \(\ds x_1 + x_2\) \(=\) \(\ds 2\)
\(\text {(2)}: \quad\) \(\ds 2 x_1 + 2 x_2\) \(=\) \(\ds 3\)

has no solutions.


Arbitrary System $3$

The system of simultaneous linear equations:

\(\text {(1)}: \quad\) \(\ds x_1 - 2 x_2 + x_3\) \(=\) \(\ds 1\)
\(\text {(2)}: \quad\) \(\ds 2 x_1 - x_2 + x_3\) \(=\) \(\ds 2\)

has as its solution set:

\(\ds x_1\) \(=\) \(\ds 1 - \dfrac t 3\)
\(\ds x_2\) \(=\) \(\ds \dfrac t 3\)
\(\ds x_3\) \(=\) \(\ds t\)

where $t$ is any number.


Arbitrary System $4$

Simultaneous Linear Equations/Examples/Arbitrary System 4

Arbitrary System $5$

Simultaneous Linear Equations/Examples/Arbitrary System 5

Arbitrary System $6$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + y + 2 z\) \(=\) \(\ds -1\)
\(\ds -x + z\) \(=\) \(\ds -1\)
\(\ds -x + y + 4 z\) \(=\) \(\ds -3\)


$S$ has as its solution set:

\(\ds x\) \(=\) \(\ds z + 1\)
\(\ds y\) \(=\) \(\ds z - 2\)

where $z$ can be any number.


Arbitrary System $7$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + 2 y + z\) \(=\) \(\ds 2\)
\(\ds -x + 2 y\) \(=\) \(\ds -1\)
\(\ds 5 x - 2 y + 2 z\) \(=\) \(\ds 7\)


$S$ has as its solution set:

\(\ds 2 x + z\) \(=\) \(\ds 3\)
\(\ds 4 y + z\) \(=\) \(\ds 1\)

where $z$ can be any number.


Arbitrary System $8$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x - y - z\) \(=\) \(\ds 1\)
\(\ds 2 x - y\) \(=\) \(\ds 1\)
\(\ds 2 x + 2 z\) \(=\) \(\ds 1\)


$S$ is inconsistent and so has no solutions.


Arbitrary System $9$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + 2 y + z\) \(=\) \(\ds 1\)
\(\ds x + y + z\) \(=\) \(\ds 1\)
\(\ds -x + z\) \(=\) \(\ds 1\)


$S$ has the single solution:

\(\ds x\) \(=\) \(\ds 0\)
\(\ds y\) \(=\) \(\ds 0\)
\(\ds z\) \(=\) \(\ds 1\)


Arbitrary System $10$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + 2 y - z + w\) \(=\) \(\ds 1\)
\(\ds 2 x + y + z\) \(=\) \(\ds 2\)


$S$ has as its solution set:

\(\ds 3 x\) \(=\) \(\ds 3 - z + w\)
\(\ds 3 y\) \(=\) \(\ds 3 z - 2 w\)

where $z$ and $w$ can be any numbers.


Arbitrary System $11$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + y - z\) \(=\) \(\ds 1\)
\(\ds y + z\) \(=\) \(\ds 2\)
\(\ds x + 2 z\) \(=\) \(\ds 1\)
\(\ds x - y + 5 z\) \(=\) \(\ds 1\)


$S$ has the single solution:

\(\ds x\) \(=\) \(\ds 0\)
\(\ds y\) \(=\) \(\ds \dfrac 3 2\)
\(\ds z\) \(=\) \(\ds \dfrac 1 2\)


Arbitrary System $12$

Let $S$ denote the system of simultaneous linear equations:

\(\ds x + 2 y + 3 z + w\) \(=\) \(\ds -1\)
\(\ds -x + y + x - w\) \(=\) \(\ds 2\)
\(\ds x + 5 y + 7 z + w\) \(=\) \(\ds 1\)


$S$ is inconsistent and so has no solutions.