### All GRE Subject Test: Math Resources

## Example Questions

### Example Question #13 : Linear Algebra

Given the following matrix, find the determinant, if possible.

**Possible Answers:**

There is no determinant.

**Correct answer:**

Write the formula to find the determinant given a 2 by 2 matrix.

Substituting in the given matrix we are able to find the determinant.

### Example Question #14 : Linear Algebra

Evaluate the determinant of the following matrix.

**Possible Answers:**

**Correct answer:**

Remember, to evaluate the determinant of a matrix use the following:

The first step would be to write the determinant of the matrix:

Now we can evaluate:

### Example Question #15 : Linear Algebra

Evaluate the determinant of the following matrix.

**Possible Answers:**

**Correct answer:**

To find the determinant of a **3 x 3 **matrix, we must use the following:

The first thing we must do is write the determinant:

Now we can proceed to evaluate the determinant

*Notice that the numbers 2, 4, and 3 are being multiplied by the determinants of the 2x2 matrices so we have:*

### Example Question #16 : Linear Algebra

Find the determinant of the matrix:

**Possible Answers:**

**Correct answer:**

Step 1: We need to recall how to find the determinant of a matrix. To find the determinant of a matrix, we need to use the equation , where =Determinant, and are from the matrix.

Step 2: Identify a,b,c, and d in the original matrix.

a=first number on top row, b=second number on top row (next to a), c=first number on the bottom row, and d is the second number on the bottom row (next to c).

In this matrix, a=, b=, c=, and d=.

Step 3: Substitute the values of a,b,c, and d into the equation to find the determinant of the matrix.

We will simplify the right side.

. We see that there are two negative signs in the middle, which will become a plus sign.

. Simplify the right side.

. is the determinant.

The determinant of the matrix is .

### Example Question #17 : Linear Algebra

Find the determinate of Matrix A.

**Possible Answers:**

**Correct answer:**

Matrix A is given below.

The formula for the determinate of a 2x2 matrix is:

Plugging in the values gives us: