Common Core: 8th Grade Math : Expressions & Equations

Study concepts, example questions & explanations for Common Core: 8th Grade Math

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Example Questions

Example Question #22 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 


8

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #21 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 

9

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #24 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 


10

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #22 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 


11

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #26 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 

5

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #23 : Use Similar Triangles To Show Equal Slopes: Ccss.Math.Content.8.Ee.B.6

Using the similar triangles, find the equation of the line in the provided graph. 


12

Possible Answers:

Correct answer:

Explanation:

The equation for a line can be written in the slope-intercept form:

,

In this equation, the variables  and  are defined as the following:

  

One way to find the slope of a line is to solve for the rise over run:

This is defined as the change in the y-axis over the change in the x axis.

The triangles in the graph provide possess two different values for their respective rise over run calculations; however, both triangle should have the same slope:

Now that we've found the slope of our line, , we can look at the graph to see where the line crosses the y-axis. The line crosses the y-axis at the following point:

Therefore, the equation of this line is,

Example Question #1 : How To Find Out When An Equation Has No Solution

Solve the rational equation:

Possible Answers:

no solution

 or 

Correct answer:

no solution

Explanation:

With rational equations we must first note the domain, which is all real numbers except  and . That is, these are the values of  that will cause the equation to be undefined. Since the least common denominator of , and  is , we can mulitply each term by the LCD to cancel out the denominators and reduce the equation to . Combining like terms, we end up with . Dividing both sides of the equation by the constant, we obtain an answer of . However, this solution is NOT in the domain. Thus, there is NO SOLUTION because  is an extraneous answer. 

Example Question #1 : How To Find Out When An Equation Has No Solution

How many solutions does the equation below have?

Possible Answers:

No solutions

Infinite 

One

Two

Three

Correct answer:

No solutions

Explanation:

When finding how many solutions an equation has you need to look at the constants and coefficients.

The coefficients are the numbers alongside the variables.

The constants are the numbers alone with no variables.

If the coefficients are the same on both sides then the sides will not equal, therefore no solutions will occur.

Use distributive property on the right side first.

           

No solutions

Example Question #3 : How To Find Out When An Equation Has No Solution

Solve:  

Possible Answers:

Correct answer:

Explanation:

First factorize the numerator.

Rewrite the equation.

The  terms can be eliminated.

Subtract one on both sides.

However, let's substitute this answer back to the original equation to check whether if we will get  as an answer.

Simplify the left side.

The left side does not satisfy the equation because the fraction cannot be divided by zero.

Therefore,  is not valid.

The answer is:  

Example Question #2 : How To Find Out When An Equation Has No Solution

Solve for :

Possible Answers:

No solution

Correct answer:

No solution

Explanation:

Combine like terms on each side of the equation:

Next, subtract  from both sides. 

Then subtract  from both sides. 

This is nonsensical; therefore, there is no solution to the equation.

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