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

Study concepts, example questions & explanations for SAT Math

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Example Questions

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Example Question #100 : Coordinate Geometry

At what point do these two lines intersect?

Possible Answers:

None of the above

Correct answer:

Explanation:

If two lines intersect, that means that at one point, the  and  values are the same. Therefore, we can use substitution to solve this problem. 

Let's substitute  in for  in the other equation. Then, solve for :

Now, we can substitute this into either equation and solve for :

With these two values, the point of intersection is 

Example Question #101 : Coordinate Geometry

At what point do these two lines intersect?

Possible Answers:

None of the given answers

Correct answer:

Explanation:

If two lines intersect, that means that their  and  values are the same at one point. Therefore, we can use substitution to solve this problem.

First, let's write these two formulas in slope-intercept form. First:

Then, for the second line:

Now, we can substitute  in for  in our second equation and solve for , like so:

Now, we can substitute this value into either equation to solve for 

Therefore, our point of intersection is 

Example Question #102 : Coordinate Geometry

Trans

Lines P and Q are parallel. Find the value of .

Possible Answers:

Correct answer:

Explanation:

Since these are complementary angles, we can set up the following equation.

 

Now we will use the quadratic formula to solve for .

 

Example Question #251 : New Sat

      Q5

The table and graph describe two different particle's travel over time. Which particle has a lower minimum?

Possible Answers:

Correct answer:

Explanation:

This question is testing one's ability to compare the properties of functions when they are illustrated in different forms. This question specifically is asking for the examination and interpretation of two quadratic functions for which one is illustrated in a table format and the other is illustrated graphically.

Step 1: Identify the minimum of the table.

Using the table find the time value where the lowest distance exists. 

Recall that the time represents the  values while the distance represents the  values. Therefore the ordered pair for the minimum can be written as .

Step 2: Identify the minimum of the graph

Recall that the minimum of a cubic function is known as a local minimum. This occurs at the valley where the vertex lies.

For this particular graph the vertex is at .

Q5

Step 3: Compare the minimums from step 1 and step 2.

Compare the  value coordinate from both minimums.

Therefore, the graph has the lowest minimum.

Example Question #104 : Coordinate Geometry

Axes

Figure NOT drawn to scale.

On the coordinate axes shown above, the shaded triangle has the following area:

Evaluate .

Possible Answers:

Correct answer:

Explanation:

The lengths of the horizontal and vertical legs of the triangle correspond to the -coordinate  of the -intercept and the -coordinate  of the -intercept. The area of a right triangle is half the product of the lengths of its legs  and . The length of the vertical leg is , so, setting  and , and solving for :

Therefore, the -intercept of the line containing the hypotenuse is . The slope of the line given the coordinates of its intercepts is 

.

substituting:

.

Substituting for  and  in the slope-intercept form of the equation of a line, 

,

the line has equation

.

Substituting  for  and 6 for  and solving for , we find the -coordinate 

of the point on the line with -coordinate 6:

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