Absolute Value - Algebra II

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Question

Screen_shot_2014-12-24_at_3.03.30_pm

What is the equation of the above function?

Answer

The formula of an absolute value function is where m is the slope, a is the horizontal shift and b is the vertical shift. The slope can be found with any two adjacent integer points, e.g. and , and plugging them into the slope formula, , yielding . The vertical and horizontal shifts are determined by where the crux of the absolute value function is. In this case, at , and those are your a and b, respectively.

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Question

Axes_1

Refer to the above figure.

Which of the following functions is graphed?

Answer

Below is the graph of :

Axes_1

The given graph is the graph of translated by moving the graph 7 units left (that is, unit right) and 2 units down (that is, units up)

The function graphed is therefore

where . That is,

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Question

Axes_1

Refer to the above figure.

Which of the following functions is graphed?

Answer

Below is the graph of :

Axes_1

The given graph is the graph of reflected in the -axis, then translated left 2 units (or, equivalently, right units. This graph is

, where .

The function graphed is therefore

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Question

Axes_1

Refer to the above figure.

Which of the following functions is graphed?

Answer

Below is the graph of :

Axes_1

The given graph is the graph of reflected in the -axis, then translated up 6 units. This graph is

, where .

The function graphed is therefore

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Question

Which of the following absolute value functions is represented by the following graph?

Answer

The equation can be determined from the graph by following the rules of transformations; the base equation is:

The graph of this base equation is:

When we compare our graph to the base equation graph, we see that it has been shifted right 3 units, up 1 unit, and our graph has been stretched vertically by a factor of 2. Following the rules of transformations, the equation for our graph is written as:

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Question

Give the vertex of the graph of the function .

Answer

Let

The graph of this basic absolute value function is a "V"-shaped graph with a vertex at the origin, or the point with coordinates . In terms of ,

The graph of this function can be formed by shifting the graph of left 6 units ( ) and down 7 units (). The vertex is therefore located at .

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Question

Give the vertex of the graph of the function .

Answer

Let

The graph of this basic absolute value function is a "V"-shaped graph with a vertex at the origin, or the point with coordinates . In terms of ,

,

or, alternatively written,

The graph of is the same as that of , after it shifts 10 units left ( ), it flips vertically (negative symbol), and it shifts up 10 units (the second ). The flip does not affect the position of the vertex, but the shifts do; the vertex of the graph of is at .

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Question

Solve the inequality:

Answer

The inequality compares an absolute value function with a negative integer. Since the absolute value of any real number is greater than or equal to 0, it can never be less than a negative number. Therefore, can never happen. There is no solution.

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Question

Solve for :

Answer

Solve for positive values by ignoring the absolute value. Solve for negative values by switching the inequality and adding a negative sign to 7.

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Question

Give the solution set for the following equation:

Answer

First, subtract 5 from both sides to get the absolute value expression alone.

Split this into two linear equations:

or

The solution set is

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Question

Solve for .

Answer

Divide both sides by 3.

Consider both the negative and positive values for the absolute value term.

Subtract 2 from both sides to solve both scenarios for .

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Question

Solve for in the inequality below.

Answer

The absolute value gives two problems to solve. Remember to switch the "less than" to "greater than" when comparing the negative term.

or

Solve each inequality separately by adding to all sides.

or

This can be simplified to the format .

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Question

Answer

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Question

Solve the inequality.

Answer

Remove the absolute value by setting the term equal to either or . Remember to flip the inequality for the negative term!

Solve each scenario independently by subtracting from both sides.

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Question

Solve for :

Answer

To solve absolute value equations, we must understand that the absoute value function makes a value positive. So when we are solving these problems, we must consider two scenarios, one where the value is positive and one where the value is negative.

and

This gives us:

and

However, this question has an outside of the absolute value expression, in this case . Thus, any negative value of will make the right side of the equation equal to a negative number, which cannot be true for an absolute value expression. Thus, is an extraneous solution, as cannot equal a negative number.

Our final solution is then

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Question

Solve for :

Answer

The absolute value of any number is nonnegative, so must always be greater than . Therefore, any value of makes this a true statement.

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Question

Solve the following absolute value inequality:

Answer

To solve this inequality, it is best to break it up into two separate inequalities to eliminate the absolute value function:

or .

Then, solve each one separately:

Combining these solutions gives:

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Question

Which values of provide the full solution set for the inequality:

Answer

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Question

An individual's heart rate during exercise is between and of the individual's maximum heart rate. The maximum heart rate of a year old is beats per minute. Express a year old's target heart rate in an absolute value equation. Note: round the and endpoints to the nearest whole number.

Answer

We start by finding the midpoint of the interval, which is enclosed by 60% of 204 and 80% of 204.

We find the midpoint, or average, of these endpoints by adding them and dividing by two:

142.5 is exactly 20.5 units away from both endpoints, 122 and 163. Since we are looking for the range of numbers between 122 and 163, all possible values have to be within 20.5 units of 142.5. If a number is greater than 20.5 units away from 142.5, either in the positive or negative direction, it will be outside of the \[122, 163\] interval. We can express this using absolute value in the following way:

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Question

In order to ride a certain roller coaster at an amusement park an individual needs to be between and pounds. Express this rule using an absolute value.

Answer

We start by finding the midpoint of the interval, which is enclosed by 90 and 210. We find the midpoint, or average, of these two endpoints by adding them and dividing by two:

150 is exactly 60 units away from both endpoints, 90 and 210. Since we are looking for the range of numbers that fall in between 90 and 210, this means that any possible value can't be more than 60 units away from 150. If a number is more than 60 units away from 150, in either the increasing or decreasing direction, it will be outside of the \[90, 210\] interval. We can express this using absolute value in the following way:

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