Algebra II : Mathematical Relationships and Basic Graphs

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #1 : Equations With Complex Numbers

If  and  are real numbers, and , what is  if ?

Possible Answers:

Correct answer:

Explanation:

To solve for , we must first solve the equation with the complex number for  and . We therefore need to match up the real portion of the compex number with the real portions of the expression, and the imaginary portion of the complex number with the imaginary portion of the expression. We therefore obtain:

 and 

We can use substitution by noticing the first equation can be rewritten as  and substituting it into the second equation. We can therefore solve for :

With this  value, we can solve for :

Since we now have  and , we can solve for :

Our final answer is therefore 

Example Question #2 : Equations With Complex Numbers

Solve for  if .

Possible Answers:

Correct answer:

Explanation:

Go about this problem just like any other algebra problem by following your order of operations. We will first evaluate what is inside the parentheses: . At this point, we need to know the properties of  which are as follows:

 

 

Therefore,  and the original expression becomes  

Example Question #1 : Equations With Complex Numbers

Evaluate and simplify .

Possible Answers:

None of the other answers.

Correct answer:

Explanation:

The first step is to evaluate the expression. By FOILing the expression, we get:

 

 

Now we need to simplify any terms that we can by using the properties of 

 

 

Therefore, the expression becomes

Example Question #5 : Equations With Complex Numbers

Solve for :

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to first simplify our equation. The first thing we should do is distribute the square, which gives us

Now  is actually just . Therefore, this becomes

Now all we need to do is solve for  in the equation:

which gives us

Finally, we get 

and therefore, our solution is

Example Question #1 : Equations With Complex Numbers

Solve for  and

Possible Answers:

Correct answer:

Explanation:

Remember that 

So the powers of  are cyclic. This means that when we try to figure out the value of an exponent of , we can ignore all the powers that are multiples of  because they end up multiplying the end result by , and therefore do nothing.

This means that 

Now, remembering the relationships of the exponents of , we can simplify this to:

Because the elements on the left and right have to correspond (no mixing and matching!), we get the relationships: 

No matter how you solve it, you get the values .

Example Question #1 : Equations With Complex Numbers

Solve

Possible Answers:

No solution

All real numbers

Correct answer:

No solution

Explanation:

To solve

Subtract  from both side:

Which is never true, so there is no solution.

Example Question #1 : Graphing Functions With Complex Numbers

Solve for 

Possible Answers:

Correct answer:

Explanation:

Use the change of base formula for logarithmic functions and incorporate the fact that  and 

Or

 can be solved using 

Example Question #1 : Graphing Functions With Complex Numbers

Where would  fall on the number line? 

Possible Answers:

to the left of 

at 

to the right of 

Cannot be determined

Correct answer:

Cannot be determined

Explanation:

Imaginary numbers do not fall on the number line-- they are by definition not real numbers. 

** If the question asked where  falls on the number line, the answer would be to the left of 0, because .

Example Question #161 : Imaginary Numbers

Write the complex number  in polar form, where polar form expresses the result in terms of a distance from the origin  on the complex plane and an angle from the positive -axis, , measured in radians.

Possible Answers:

Correct answer:

Explanation:

To see what the polar form of the number is, it helps to draw it on a graph, where the horizontal axis is the imaginary part and the vertical axis the real part. This is called the complex plane.

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To find the angle , we can find its supplementary angle  and subtract it from  radians, so .

Using trigonometric ratios,    and  .

Then .

 

To find the distance , we need to find the distance from the origin to the point . Using the Pythagorean Theorem to find the hypotenuse  or .

Example Question #2 : Graphing Functions With Complex Numbers

Where does  fall on the number line?

Possible Answers:

To the right of 0

To the left of 0

At 0

Cannot be determined

Correct answer:

To the left of 0

Explanation:

 Imaginary numbers do not fall on the number line by definition, since they are not real numbers. However, although i is an imaginary number equal to the square root of -1,  is a real number since . Therefore, . Negative numbers fall to the left of 0 on a number line.

 

 

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