ACT Math : How to find out if a point is on a line with an equation

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #714 : Act Math

Consider the lines described by the following two equations:

4y = 3x2

 

3y = 4x2

Find the vertical distance between the two lines at the points where x = 6.

Possible Answers:

21

12

44

48

36

Correct answer:

21

Explanation:

Since the vertical coordinates of each point are given by y, solve each equation for y and plug in 6 for x, as follows:

Taking the difference of the resulting -values give the vertical distance between the points (6,27) and (6,48), which is 21.

Example Question #106 : Geometry

For the line

Which one of these coordinates can be found on the line?

Possible Answers:

(9, 5)

(6, 5)

(6, 12)

(3, 7)

(3, 6)

Correct answer:

(3, 6)

Explanation:

To test the coordinates, plug the x-coordinate into the line equation and solve for y.

y = 1/3x -7

Test (3,-6)

y = 1/3(3) – 7 = 1 – 7 = -6   YES!

Test (3,7)

y = 1/3(3) – 7 = 1 – 7 = -6  NO

Test (6,-12)

y = 1/3(6) – 7 = 2 – 7 = -5  NO

Test (6,5)

y = 1/3(6) – 7 = 2 – 7 = -5  NO

Test (9,5)

y = 1/3(9) – 7 = 3 – 7 = -4  NO

Example Question #715 : Act Math

Solve the following system of equations:

–2x + 3y = 10

2x + 5y = 6

Possible Answers:

(3, –2)

(2, 2)

(–2, –2)

(–2, 2)

(3, 5)

Correct answer:

(–2, 2)

Explanation:

Since we have –2x and +2x in the equations, it makes sense to add the equations together to give 8y = 16 yielding y = 2.  Then we substitute y = 2 into one of the original equations to get x = –2.  So the solution to the system of equations is (–2, 2)

Example Question #93 : Coordinate Geometry

Which of the following sets of coordinates are on the line y=3x-4?

Possible Answers:

(1,2)

(2,2)

(2,-2)

(3,4)

(1,5)

Correct answer:

(2,2)

Explanation:

(2,2) when plugged in for y and x make the linear equation true, therefore those coordinates fall on that line.

y=3x-4

Because this equation is true, the point must lie on the line. The other given answer choices do not result in true equalities.

Example Question #716 : Act Math

Which of the following points can be found on the line \small y=3x+2?

Possible Answers:

Correct answer:

Explanation:

We are looking for an ordered pair that makes the given equation true. To solve, plug in the various answer choices to find the true equality.

Because this equality is true, we can conclude that the point lies on this line. None of the other given answer options will result in a true equality.

Example Question #2 : How To Find Out If A Point Is On A Line With An Equation

Which of the following points is on the line ?

Possible Answers:

Correct answer:

Explanation:

The only thing that is necessary to solve this question is to see if a given  value will provide you with the  value paired with it. Among the options provided, only  works. This is verified by the following simple substitution:

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