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Question 5 (Essay Worth 4 points)

The matrix equation represents a system of equations.

A matrix with 2 rows and 2 columns, where row 1 is 2 and 7 and row 2 is 2 and 6, is multiplied by matrix with 2 rows and 1 column, where row 1 is x and row 2 is y, equals a matrix with 2 rows and 1 column, where row 1 is 8 and row 2 is 6.

Solve for y using matrices. Show or explain all necessary steps.

Answer 1

The given matrix equation can be written as:

[2 7; 2 6] * [x; y] = [8; 6]

Multiplying the matrices on the left side of the equation gives us the system of equations:

2x + 7y = 8 2x + 6y = 6

To solve for x and y using matrices, we can use the inverse matrix method. First, we need to find the inverse of the coefficient matrix [2 7; 2 6]. The inverse of a 2x2 matrix [a b; c d] can be calculated using the formula: (1/(ad-bc)) * [d -b; -c a].

Let’s apply this formula to our coefficient matrix:

The determinant of [2 7; 2 6] is (26) - (72) = -2. Since the determinant is not equal to zero, the inverse of the matrix exists and can be calculated as:

(1/(-2)) * [6 -7; -2 2] = [-3 7/2; 1 -1]

Now we can use this inverse matrix to solve for x and y. Multiplying both sides of our matrix equation by the inverse matrix gives us:

[-3 7/2; 1 -1] * [2x + 7y; 2x + 6y] = [-3 7/2; 1 -1] * [8; 6]

Solving this equation gives us:

[x; y] = [-1; 2]

So, the solution to the system of equations is x = -1 and y = 2.