SAT Math : Other Lines

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #140 : Coordinate Geometry

Which line contains the following ordered pairs:

 and

Possible Answers:

\small y=\frac{1}{4}x+\frac{7}{2}

\small y=-x+14

\small y=x+14

\small y=-\frac{1}{4}x+\frac{7}{2}

Correct answer:

\small y=-\frac{1}{4}x+\frac{7}{2}

Explanation:

First, solve for slope.

\small m=\frac{\Delta y}{\Delta x}=\frac{2-4}{6-(-2)}=\frac{-2}{8}=-\frac{1}{4}

Then, substitute one of the points into the equation y=mx+b.

\small 2=(-\frac{1}{4})(6)+b

\small 2=(-\frac{3}{2})+b

\small b=2+\frac{3}{2}=\frac{7}{2}

This leaves us with the equation \small y=-\frac{1}{4}+\frac{7}{2}

Example Question #1 : How To Find The Equation Of A Line

Given the graph of the line below, find the equation of the line.

 

Act_math_160_04

Possible Answers:

Correct answer:

Explanation:

To solve this question, you could use two points such as (1.2,0) and (0,-4) to calculate the slope which is 10/3 and then read the y-intercept off the graph, which is -4.

 

Example Question #241 : Geometry

Which line passes through the points (0, 6) and (4, 0)?

Possible Answers:

y = 1/5x + 3

y = 2/3x –6

y = –3/2 – 3

y = 2/3 + 5

y = –3/2x + 6

Correct answer:

y = –3/2x + 6

Explanation:

P1 (0, 6) and P2 (4, 0)

First, calculate the slope:  m = rise ÷ run = (y2 – y1)/(x– x1), so m = –3/2

Second, plug the slope and one point into the slope-intercept formula: 

y = mx + b, so 0 = –3/2(4) + b and b = 6

Thus, y = –3/2x + 6

Example Question #1 : Coordinate Geometry

What line goes through the points (1, 3) and (3, 6)?

Possible Answers:

–2x + 2y = 3

4x – 5y = 4

–3x + 2y = 3

2x – 3y = 5

3x + 5y = 2

Correct answer:

–3x + 2y = 3

Explanation:

If P1(1, 3) and P2(3, 6), then calculate the slope by m = rise/run = (y2 – y1)/(x2 – x1) = 3/2

Use the slope and one point to calculate the intercept using y = mx + b

Then convert the slope-intercept form into standard form.

Example Question #144 : Coordinate Geometry

What is the slope-intercept form of \dpi{100} \small 8x-2y-12=0?

Possible Answers:

\dpi{100} \small y=-2x+3

\dpi{100} \small y=4x-6

\dpi{100} \small y=-4x+6

\dpi{100} \small y=4x+6

\dpi{100} \small y=2x-3

Correct answer:

\dpi{100} \small y=4x-6

Explanation:

The slope intercept form states that \dpi{100} \small y=mx+b. In order to convert the equation to the slope intercept form, isolate \dpi{100} \small y on the left side:

\dpi{100} \small 8x-2y=12

\dpi{100} \small -2y=-8x+12

\dpi{100} \small y=4x-6

Example Question #61 : Coordinate Geometry

A line is defined by the following equation:

What is the slope of that line?

Possible Answers:

Correct answer:

Explanation:

The equation of a line is

y=mx + b where m is the slope

Rearrange the equation to match this:

7x + 28y = 84

28y = -7x + 84

y = -(7/28)x + 84/28

y = -(1/4)x + 3

m = -1/4

Example Question #1 : Lines

If the coordinates (3, 14) and (5, 15) are on the same line, what is the equation of the line?

Possible Answers:

Correct answer:

Explanation:

First solve for the slope of the line, m using y=mx+b

m = (y2 – y1) / (x2 – x1)

= (15  14) / (5 3)

= (1 )/( 8)

=1/8

y = (1/8)x + b

Now, choose one of the coordinates and solve for b:

14 = (1/8)3 + b

14 = 3/8 + b

b = 14 + (3/8)

b = 14.375

y = (1/8)x + 14.375

Example Question #1 : Coordinate Geometry

What is the equation of a line that passes through coordinates \dpi{100} \small (2,6) and \dpi{100} \small (3,5)?

Possible Answers:

\dpi{100} \small y=x+7

\dpi{100} \small y=-x+8

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

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

\dpi{100} \small y=3x+2

Correct answer:

\dpi{100} \small y=-x+8

Explanation:

Our first step will be to determing the slope of the line that connects the given points.

Our slope will be . Using slope-intercept form, our equation will be . Use one of the give points in this equation to solve for the y-intercept. We will use \dpi{100} \small (2,6).

Now that we know the y-intercept, we can plug it back into the slope-intercept formula with the slope that we found earlier.

This is our final answer.

Example Question #61 : Lines

Which of the following equations does NOT represent a line?

Possible Answers:

Correct answer:

Explanation:

The answer is .

A line can only be represented in the form  or , for appropriate constants , , and . A graph must have an equation that can be put into one of these forms to be a line.

 represents a parabola, not a line. Lines will never contain an term.

Example Question #2 : Lines

Let y = 3x – 6.

At what point does the line above intersect the following:

 

 

Possible Answers:

(–3,–3)

(–5,6)

They do not intersect

(0,–1)

They intersect at all points

Correct answer:

They intersect at all points

Explanation:

If we rearrange the second equation it is the same as the first equation. They are the same line.

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