Use determinants and the inverse to solve the system of equations:

[tex]\[
\begin{array}{l}
3x + 2y + 2 = 6 \\
x - 2y + 32 = 2 \\
5x + 2y - 42 = 3
\end{array}
\][/tex]



Answer :

Sure! Let's solve the given system of linear equations using determinants and the inverse of the coefficient matrix.

The system of equations is:
[tex]\[ \begin{aligned} 3x + 2y + 2 &= 6, \\ x - 2y + 32 &= 2, \\ 5x + 2y - 42 &= 3. \end{aligned} \][/tex]

First, we need to rewrite each equation in the standard form [tex]\(Ax = B\)[/tex], where [tex]\(A\)[/tex] is the matrix of coefficients, [tex]\(x\)[/tex] is the column matrix of variables, and [tex]\(B\)[/tex] is the column matrix of constants.

Rewriting the equations:
[tex]\[ \begin{aligned} 3x + 2y &= 4, \\ x - 2y &= -30, \\ 5x + 2y &= 45. \end{aligned} \][/tex]

The coefficient matrix [tex]\(A\)[/tex] and constants matrix [tex]\(B\)[/tex] are:
[tex]\[ A = \begin{pmatrix} 3 & 2 \\ 1 & -2 \\ 5 & 2 \end{pmatrix}, \quad B = \begin{pmatrix} 4 \\ -30 \\ 45 \end{pmatrix} \][/tex]

Since this is a 3x3 system, let's set up the augmented matrix and proceed using the inverse matrix method:

1. Find the determinant of [tex]\(A\)[/tex]:

The determinant of a matrix [tex]\(A\)[/tex] is denoted as [tex]\(|A|\)[/tex] and for a 3x3 matrix, it is calculated as follows:

[tex]\[ |A| = \begin{vmatrix} 3 & 2 & 0 \\ 1 & -2 & 0 \\ 5 & 2 & 0 \end{vmatrix} \][/tex]

To find the determinant, let's expand along the third column (noting that the elements in the third column are all zeros). With all zeros in one column, the determinant of matrix [tex]\(A\)[/tex] is:

[tex]\[ |A| = 0 \][/tex]

A determinant of zero implies that the matrix [tex]\(A\)[/tex] is singular, which means it does not have an inverse. Therefore, the system of equations does not have a unique solution; it may either have no solution or an infinite number of solutions.

Since the determinant is zero, we face a special case. Let’s look into a deeper scrutiny:

2. Determine if the system has infinitely many solutions or no solution:

To do this, we can convert the system into row-echelon form and check for consistency.

[tex]\[ \begin{aligned} 3x + 2y &= 4 &\quad (1) \\ x - 2y &= -30 &\quad (2) \\ 5x + 2y &= 45 &\quad (3) \end{aligned} \][/tex]

Let's eliminate [tex]\(y\)[/tex] from equations (1) and (3):

From equation (2): [tex]\( x = -30 + 2y \)[/tex].

Substitute [tex]\(x\)[/tex] in equations (1) and (3):
[tex]\[ \begin{aligned} 3(-30 + 2y) + 2y &= 4 \\ -90 + 6y + 2y &= 4 \\ 8y &= 94 \\ y &= \frac{94}{8} = 11.75 \end{aligned} \][/tex]

Substitute [tex]\(y = 11.75\)[/tex] back into [tex]\(x = -30 + 2y\)[/tex]:

[tex]\[ x = -30 + 2(11.75) = -30 + 23.5 = -6.5 \][/tex]

Let's check this solution in the third equation:
[tex]\[ 5(-6.5) + 2(11.75) = -32.5 + 23.5 = -9 \][/tex]

This seems to yield a contradiction as the calculated value does not satisfy the third equation. Therefore, revising the steps show the system doesn't have a consistent solution, concluding the discussed system of equations does not provide a correct solution with the set values.

However, knowing that determinant of zero suggests parallel or overly determined system needing more breed calculation effort.

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