ORCA Units 3&4

Which of the following is true about identity and inverse matrices?

• A matrix multiplied by it's inverse is the identity matrix.

• A matrix multiplied by it's identity is the inverse matrix.

What is the value of a₂₁ of the difference?

Find the product.

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After multiplying the scalar, what is the element in row 3?

When can you NOT multiply 2 matrices together?

• When the first matrices' row is not equal to the second matrices' column.

• When the first matrices' column is not equal to the second matrices' row.

• When the first matrices' column is not equal to the second matrices' column.

• When the first matrices' row is not equal to the second matrices' row.

• They can always be multiplied together since it is commutative.

Find the inverse using the formula.

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• No inverse exists.

Find the determinant.

Answer explanation

det(A) = ad - bc

What does it mean when the determinant is zero?

• The system has 1 solution. (Independent and Consistent)

• The system has infinite solutions. (Dependent and Consistent)

• The system has no solution. (Dependent and Inconsistent)

To be able to find the determinant of a matrix...

• it must be a square matrix

• it must have more rows than columns

• it must have more columns than rows

Describe rref for this matrix. Select all that apply.

• The 4 and 1 need to become 1's

• the -3 and -6 need to become 0's

• the last column is for the solution set

• Add multiple of other rows to get 0's and multiply scalars to get 1's

• Add multiple of other rows to get 1's and multiply scalars to get 0's