ACT Math : Algebra

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #3 : How To Graph A Function

Which of the following graphs represents the y-intercept of this function?

Possible Answers:

Function_graph_2

Function_graph_3

Function_graph_1

Function_graph_4

Correct answer:

Function_graph_1

Explanation:

Graphically, the y-intercept is the point at which the graph touches the y-axis.  Algebraically, it is the value of  when .

Here, we are given the function .  In order to calculate the y-intercept, set  equal to zero and solve for .

So the y-intercept is at .

Example Question #15 : How To Graph A Function

Which of the following graphs represents the x-intercept of this function?

Possible Answers:

Function_graph_5

Function_graph_6

Function_graph_7

Function_graph_8

Correct answer:

Function_graph_6

Explanation:

Graphically, the x-intercept is the point at which the graph touches the x-axis.  Algebraically, it is the value of  for which .

Here, we are given the function .  In order to calculate the x-intercept, set  equal to zero and solve for .

So the x-intercept is at .

Example Question #4 : How To Graph A Function

Which of the following represents ?

Possible Answers:

Function_graph_10

Function_graph_9

Function_graph_11

Function_graph_12

Correct answer:

Function_graph_9

Explanation:

A line is defined by any two points on the line.  It is frequently simplest to calculate two points by substituting zero for x and solving for y, and by substituting zero for y and solving for x.

Let .  Then

So our first set of points (which is also the y-intercept) is 

Let .  Then

So our second set of points (which is also the x-intercept) is .

Example Question #1 : How To Graph A Function

Suppose

To obtain the graph of , shift the graph  a distance of  units              .

Possible Answers:

Up and right

To the left

To the right

Upwards

Downwards

Correct answer:

Upwards

Explanation:

There are four shifts of the graph y = f(x):

y = f(x) + c shifts the graph c units upwards.

y = f(x) – c shifts the graph c units downwards.

y = f(x + c) shifts the graph c units to the left.

y = f(x – c) shifts the graph c units to the right.

Example Question #171 : Graphing

Which of the following graphs does NOT represent a function?

Possible Answers:

Act_math_159_13

Act_math_159_14

Act_math_159_10

All of the graphs are functions.

Act_math_159_12

Correct answer:

Act_math_159_13

Explanation:

This question relies on both the vertical-line test and the definition of a function. We need to use the vertical-line test to determine which of the graphs is not a function (i.e. the graph that has more than one output for a given input). The vertical-line test states that a graph represents a function when a vertical line can be drawn at every point in the graph and only intersect it at one point; thus, if a vertical line is drawn in a graph and it intersects that graph at more than one point, then the graph is not a function. The circle is the only answer choice that fails the vertical-line test, and so it is not a function.

Example Question #1 : How To Graph A Point

How would you plot the point ?

Possible Answers:

From the origin, go right  units, and up  units

From the origin, go up  units, and right  units

From the origin, go left  units, and up  units

From the origin, go right  units, and down  units

Correct answer:

From the origin, go right  units, and up  units

Explanation:

For the ordered pair 

The first number is for the x-axis, so because it is positive you go right .

The second number is for the y-axis, so because it is positive you go up .

Example Question #2 : How To Graph A Point

How would you plot the point ?

Possible Answers:

From the origin, go left  units, and up  units

 

From the origin, go right  units, and up  units

 

From the origin, go left  units, and down  units

 

From the origin, go right  units, and down  units

 

Correct answer:

From the origin, go left  units, and up  units

 

Explanation:

For the ordered pair  we would do the following.

The first number is for the x-axis, so because it is negative you go left  units.

The second number is for the y-axis, so because it is positive you go up  units.

Example Question #3 : How To Graph A Point

In which Quadrant is the point  located?

Possible Answers:

Quadrant I

Quadrant III

Quadrant II

Quadrant IV

Correct answer:

Quadrant III

Explanation:

To find out which quadrant a point lives in, we need to remember the qualities of each quadrant. By qualities, I mean the signs associated with the x and y values which are dependent on the quadrant the point resides in.

All coordinate pairs that are in Quadrant I will have a positive x value and a positive y value.

All coordinate pairs that are in Quadrant II will have a negative x value and a positive y value.

All coordinate pairs that are in Quadrant III will have a negative x value and a negative y value.

All coordinate pairs that are in Quadrant IV will have a positive x value and a negative y value.

For the point  we see that both the x and y values are negative therefore, the point lies in the third quadrant. We can also check this by starting from the origin and going left 3 units and down 3 units. This will end up in the lower-left section of the coordinate-plane, which is Quadrant III.

Example Question #1 : How To Graph A Point

What are the coordinates of point B?

Graph1

Possible Answers:

Correct answer:

Explanation:

Find the x-coordinate by going right on the horizontal x-axis until you come across the line that is directly under the point. The x-coordinate is .

Now, continue up until you reach the point and look across to the vertical y-axis. The y-coordinate is .

 is then the coordinate of the point.

Example Question #2 : How To Graph A Point

What are the coordinates for point A?

Graph2

Possible Answers:

Correct answer:

Explanation:

Find the x-coordinate by going right on the horizontal x-axis until you come across the line that is directly under the point. The x-coordinate is .

Now, continue up until you reach the point and look across to the vertical y-axis. The y-coordinate is .

 are the coordinates for point A.

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