### All Algebra II Resources

## Example Questions

### Example Question #1 : Graphing Parabolas

All of the following are equations of down-facing parabolas EXCEPT:

**Possible Answers:**

**Correct answer:**

A parabola that opens downward has the general formula

,

as the negative sign in front of the term makes flips the parabola about the horizontal axis.

By contrast, a parabola of the form rotates about the vertical axis, not the horizontal axis.

Therefore, is not the equation for a parabola that opens downward.

### Example Question #2 : Graphing Parabolas

Consider the equation:

The vertex of this parabolic function would be located at:

**Possible Answers:**

**Correct answer:**

For any parabola, the general equation is

, and the x-coordinate of its vertex is given by

.

For the given problem, the x-coordinate is

.

To find the y-coordinate, plug into the original equation:

Therefore the vertex is at .

### Example Question #3 : Graphing Parabolas

In which direction does graph of the parabola described by the above equation open?

**Possible Answers:**

up

left

right

down

**Correct answer:**

right

Parabolas can either be in the form

for vertical parabolas or in the form

for horizontal parabolas. Since the equation that the problem gives us has a y-squared term, but not an x-squared term, we know this is a horizontal parabola. The rules for a horizontal parabola are as follows:

- If
- If , then the horizontal parabola opens to the left.

In this case, the coefficient in front of the y-squared term is going to be positive, once we isolate x. That makes this a horizontal parabola that opens to the right.

### Example Question #4 : Graphing Parabolas

Find the vertex form of the following quadratic equation:

**Possible Answers:**

**Correct answer:**

Factor 2 as GCF from the first two terms giving us:

Now we complete the square by adding 4 to the expression inside the parenthesis and subtracting 8 ( because ) resulting in the following equation:

which is equal to

Hence the vertex is located at

### Example Question #1 : How To Graph A Quadratic Function

Which is the graph of ?

**Possible Answers:**

**Correct answer:**

Think of the graph of :

Constants within the parentheses will shift the parabola to the left and right, while terms outside of the parentheses will shift it vertically.

In our equation, there is a -2 term outside the parentheses. This will shift the graph down by 2 units.

The graph of will look like this:

There is also a constant within the parentheses, –1. This will shift the graph to the right by 1 unit.

Therefore will generate a graph like this:

### Example Question #1 : Quadratic Functions

**Possible Answers:**

None of them

Green line

Blue line

Purple line

Red line

**Correct answer:**

Red line

A parabola is one example of a quadratic function, regardless of whether it points upwards or downwards.

The red line represents a quadratic function and will have a formula similar to .

The blue line represents a linear function and will have a formula similar to .

The green line represents an exponential function and will have a formula similar to .

The purple line represents an absolute value function and will have a formula similar to .

### Example Question #5 : Graphing Parabolas

Which of the following parabolas is downward facing?

**Possible Answers:**

**Correct answer:**

We can determine if a parabola is upward or downward facing by looking at the coefficient of the term. It will be downward facing if and only if this coefficient is negative. Be careful about the answer choice . Recall that this means that the entire value inside the parentheses will be squared. And, a negative times a negative yields a positive. Thus, this is equivalent to . Therefore, our answer has to be .

### Example Question #35 : Functions And Lines

What is the vertex of the function ? Is it a maximum or minimum?

**Possible Answers:**

; minimum

; maximum

; maximum

; minimum

**Correct answer:**

; minimum

The equation of a parabola can be written in vertex form: .

The point in this format is the vertex. If is a postive number the vertex is a minimum, and if is a negative number the vertex is a maximum.

In this example, . The positive value means the vertex is a minimum.

### Example Question #6 : Graphing Parabolas

How many -intercepts does the graph of the function

have?

**Possible Answers:**

Two

Zero

Four

None of these

One

**Correct answer:**

Zero

The graph of a quadratic function has an -intercept at any point at which , so, first, set the quadratic expression equal to 0:

The number of -intercepts of the graph is equal to the number of real zeroes of the above equation, which can be determined by evaluating the discriminant of the equation, . Set , and evaluate:

The discriminant is negative, so the equation has two solutions, neither of which are real. Consequently, the graph of the function has no -intercepts.

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