SAT II Math II : Mathematical Relationships

Study concepts, example questions & explanations for SAT II Math II

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Example Questions

Example Question #2 : Matrices

If , what is ?

Possible Answers:

Correct answer:

Explanation:

Begin by distributing the fraction through the matrix on the left side of the equation. This will simplify the contents, given that they are factors of :

Now, this means that your equation looks like:

This simply means:

and

 or 

Therefore, 

Example Question #101 : Mathematical Relationships

Evaluate .

Possible Answers:

Correct answer:

Explanation:

The element in row , column , of  can be found by multiplying row  of  by row  of  - that is, by multiplying elements in corresponding positions and adding the products. Therefore, 

Example Question #102 : Mathematical Relationships

The determinant of this matrix is equal to 4. Evaluate .

Possible Answers:

Correct answer:

Explanation:

A matrix  has as its determinant . Setting , this becomes 

Set this determinant equal to 4 and solve for :

the correct response.

Example Question #103 : Mathematical Relationships

Let .

Which of the following real value(s) of  makes  a matrix without an inverse?

Possible Answers:

There are two such values:  and 

There is one such value: 

There is one such value: 

 has an inverse for all real values of 

There are two such values:  and 

Correct answer:

There are two such values:  and 

Explanation:

A matrix  lacks an inverse if and only if its determinant  is equal to zero. The determinant of  is 

.

Setting this equal to 0:

Taking the square root of both sides:

The matrix therefore has no inverse if either  or .

Example Question #104 : Mathematical Relationships

Let  be the two-by-two identity matrix and .

Which matrix is equal to the inverse of ?

Possible Answers:

 does not have an inverse.

Correct answer:

Explanation:

; the two-by-two identity matrix is . Add the two by adding elements in corresponding positions:

.

The inverse of a two-by-two matrix  is , where 

.

We can find  by setting . The determinant of  is

Replacing:

;

simplifying the fractions, this is 

 

Example Question #21 : Matrices

Let  and .

Evaluate .

Possible Answers:

 does not exist.

Correct answer:

Explanation:

The inverse  of any two-by-two matrix  can be found according to this pattern:

If 

then 

,

where determinant  is equal to .

Therefore, if , then , the first row/first column entry in the matrix , can be found by setting , then evaluating:

Example Question #105 : Mathematical Relationships

For which of the following real values of  does  have determinant of sixteen?

Possible Answers:

 or 

None of these

 or 

Correct answer:

 or 

Explanation:

A matrix  lacks an inverse if and only if its determinant  is equal to zero. The determinant of  is

We seek the value of  that sets this quantity equal to 16. Setting it as such then solving for :

Therefore, either  or .

Example Question #21 : Matrices

Let  equal the following:

.

Which of the following values of  makes  a matrix without an inverse?

Possible Answers:

There are two such values:  or 

There is one such value: 

There are two such values:  or 

There is one such value: 

There is one such value: 

Correct answer:

There is one such value: 

Explanation:

A matrix  lacks an inverse if and only if its determinant  is equal to zero. The determinant of  is

Set this equal to 0 and solve for :

,

the only such value.

Example Question #1 : Sequences

Evaluate: 

Possible Answers:

The series diverges

Correct answer:

The series diverges

Explanation:

An infinite series  converges to a sum if and only if . However, in the series , this is not the case, as . This series diverges.

Example Question #2 : Sequences

Give the next term in this sequence:

_______________

Possible Answers:

Correct answer:

Explanation:

The key to finding the next term lies in the denominators of the third term onwards. They are terms of the Fibonacci sequence, which begin with the terms 1 and 1 and whose subsequent terms are each formed by adding the previous two.

The th term of the sequence is the number , where  is the th number in the Fibonacci sequence (since the first two Fibonacci numbers are both 1, the first two terms being 0 fits this pattern). The Fibonacci number following 13 and 21 is their sum, 34, so the next number in the sequence is

.

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