Chapter 4: Q28. (page 199)

Find the inverse of each matrix, if it exists.28.
$[\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$

Short Answer

Expert verified

The inverse of the matrix is does not exist.

Step by step solution

- Define inverse of a matrix.

For the matrix A ,

$A = [\begin{matrix} a & b \\ c & d \end{matrix}]$

The inverse of matrix of the matrix A is:

$A^{- 1} = \frac{1}{a d - b c} [\begin{matrix} d & - b \\ - c & a \end{matrix}]$

where $a d - b c \neq 0$ . $a d - b c$ is the determinant of the matrix A .

If $a d - b c = 0$ , the inverse of a matrix doesn not exist.

- Calculate the inverse.

Let be the matrix $[\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$

That is, $A = [\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$

Comparing with the standard form $A = [\begin{matrix} a & b \\ c & d \end{matrix}]$ , $a = - 4, b = 6, c = 6, d = - 9$ .

Then, $A^{- 1}$ is:

$\begin{matrix} A^{- 1} = \frac{1}{a d - b c} [\begin{matrix} d & - b \\ - c & a \end{matrix}] \\ = \frac{1}{(- 4 \times - 9) - (6 \times 6)} [\begin{matrix} - 9 & - 6 \\ - 6 & - 4 \end{matrix}] \\ = \frac{1}{36 - 36} [\begin{matrix} - 9 & - 6 \\ - 6 & - 4 \end{matrix}] \end{matrix}$

Here, $\begin{matrix} a d - b c = 36 - 36 \\ = 0 \end{matrix}$

And inverse exist only if $a d - b c \neq 0$ .

As $a d - b c = 0$ here, inverse doesnot exist.

- State the conclusion.

Therefore, the inverse of the matrix $[\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$ does not exist.

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Find the inverse of each matrix, if it exists.28.
$[\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$

Short Answer

Step by step solution

- Define inverse of a matrix.

- Calculate the inverse.

- State the conclusion.

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Find the inverse of each matrix, if it exists.28.[−466−9]

Short Answer

Step by step solution

- Define inverse of a matrix.

- Calculate the inverse.

- State the conclusion.

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Math Textbooks

Mechanics Maths

Decision Maths

Logic and Functions

Applied Mathematics

Pure Maths

Theoretical and Mathematical Physics

Study anywhere. Anytime. Across all devices.

Find the inverse of each matrix, if it exists.28.
$[\begin{matrix} - 4 & 6 \\ 6 & - 9 \end{matrix}]$