SAT Math : How to graph a line

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #1 : Graphing

A line graphed on the coordinate plane below. Graph_of_y_-2x_4

Give the equation of the line in slope intercept form. 

Possible Answers:

\dpi{100} \small y=-2x+4

\dpi{100} \small y=-2x-4

\dpi{100} \small y=2x-4

\dpi{100} \small y=2x+4

\dpi{100} \small y=-x+4

Correct answer:

\dpi{100} \small y=-2x+4

Explanation:

The slope of the line is \dpi{100} \small -2 and the y-intercept is \dpi{100} \small 4.

The equation of the line is \dpi{100} \small y=-2x+4

Example Question #2 : Graphing

Graph_of_y_-x_3

Give the equation of the curve. 

Possible Answers:

\dpi{100} \small y=x^{4}

\dpi{100} \small y=-x^{2}

None of the other answers

\dpi{100} \small y=x^{3}

\dpi{100} \small y=-x^{3}

Correct answer:

\dpi{100} \small y=-x^{3}

Explanation:

Graph_of_x_3This is the parent graph of \dpi{100} \small x^{3}. Since the graph in question is negative, then we flip the quadrants in which it will approach infinity. So the graph of \dpi{100} \small y=-x^{3} will start in quadrant 2 and end in 4. 

Example Question #1 : How To Graph A Line

Give the area of the triangle on the coordinate plane that is bounded by the lines of the equations  and .

Possible Answers:

Correct answer:

Explanation:

It is necessary to find the coordinates of the vertices of the triangle, each of which is the intersection of two of the three lines.

The intersection of the lines of the equations  and  can be found by noting that, by substituting   for  in the latter equation, , making the point of intersection .

 

The intersection of the lines of the equations  and  can be found by substituting   for  in the latter equation and solving for :

This point of intersection is .

 

 

The intersection of the lines of the equations  and  can be found by substituting   for  in the latter equation and solving for :

Since , and this point of intersection is .

The lines in question are graphed below, and the triangle they bound is shaded:

Triangle z

We can take the horizontal side as the base of the triangle; its length is the difference of the -coordinates:

The height is the vertical distance from this side to the opposite side, which is the difference of the -coordinates:

The area is half their product:

Example Question #285 : Geometry

Billy set up a ramp for his toy cars. He did this by taking a wooden plank and putting one end on top of a brick that was 3 inches high. He then put the other end on top of a box that was 9 inches high. The bricks were 18 inches apart. What is the slope of the plank?

Possible Answers:

Correct answer:

Explanation:

The value of the slope (m) is rise over run, and can be calculated with the formula below:

The coordinates of the first end of the plank would be (0,3), given that this is the starting point of the plank (so x would be 0), and y would be 3 since the brick is 3 inches tall. 

The coordinates of the second end of the plank would be (18,9) since the plank is 18 inches long (so x would be 18) and y would be 9 since the box was 9 inches tall at the other end. 

From this information we know that we can assign the following coordinates for the equation:

 and 

Below is the solution we would get from plugging this information into the equation for slope:

This reduces to 

 

Example Question #671 : Geometry

What is the slope of the line depicted by the graph?

Screen shot 2016 02 10 at 9.35.05 am

Possible Answers:

Correct answer:

Explanation:

Looking at the graph, it is seen that the line passes through the points (-8,-5) and (8,5).

Screen shot 2016 02 10 at 9.35.05 am

The slope of a line through the points  and  can be found by setting 

:

in the slope formula:

 

Example Question #282 : Coordinate Geometry

Screen shot 2016 01 12 at 2.32.17 pm

What is the -intercept of the function that is depicted in the graph above?

Possible Answers:

Correct answer:

Explanation:

This question tests one's ability to recognize algebraic characteristics of a graph. This particular question examines a linear function.

Knowing the standard and the concept for which it relates to, we can now do the step-by-step process to solve the problem in question.

Step 1: Identify the general algebraic function for the given graph.

Since the graph is that of a straight line, the general algebraic form of the function is,

where

Step 2: Identify where the graph crosses the -axis.

Screen shot 2016 01 12 at 2.32.17 pm

Therefore the general form of the function looks like,

Step 3: Answer the question.

The -intercept is three.

Example Question #673 : Geometry

The equation  represents a line.  This line does NOT pass through which of the four quadrants?

Possible Answers:

II

IV

III

I

Cannot be determined

Correct answer:

III

Explanation:

Plug in  for  to find a point on the line:

Thus,  is a point on the line.

Plug in   for  to find a second point on the line:

 is another point on the line.

Now we know that the line passes through the points  and .  

A quick sketch of the two points reveals that the line passes through all but the third quadrant.

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