Proportional Graphs

Proportional Graphs

by Stefany Kemp

​Let's Look at y=kx

​In this formula the y and x are our values for our graphing coodinates (x,y).

​

​Suppose we are given our k or constant value in the formula:

​​y=2x

Because we know the k or constant value it is easy to graph our points

​

Multiple Choice

y=kx

​Suppose we are given our k or constant value in the formula:

​​y=2x

We know the k or constant value is 2. Where will we get the values for x?

• The values on the y-axis of the graph.

• The values on the x-axis of the graph.

Draw

Plot the lines for a proportional graph if the k, constant is 2.

y=2x

​What if we aren't give the value for k (constant) and we are just given the graph?

​We know that in the graph we have the x and y values for our formula, from our x-axis and our y-axis.

y=kx.

​

​Let's plug the point (1,2) into the formula. 2=k(1)

​- In order to solve we need to move the 1 to get k on one side of the equation.

​

​How do we get k by itslef?

Multiple Choice

How do we get k by itself?

2=k(1)

• Add 1 to both sides

• Subtract 1 from both sides

• Multiply 1 to both sides

• Divide 1 on both sides

​What if we aren't give the value for k (constant) and we are just given the graph?

​How do we find the consant?

​​Let's plug the point (1,2) into the formula. 2=k(1)

​- In order to solve we need to move the 1 to get k on one side of the equation.

​- Divide 1 on each side of the equation to get k by itslef:

​2/1=k(1)/1

​*This gives us the the formual k=y/x​

2/1=k​

​

​

​What if we aren't give the value for k (constant) and we are just given the graph?

​How do we find the consant?

​- Point (1,2)

​2/1=k(1)/1

2/1=k

k=2​

​

​Use the formula k=y/x to see if points (2,4) and (3,6) equal the same value for k.

Poll

Do they equal the same value for k?

• Yes

• N

​What if we aren't give the value for k (constant) and we are just given the graph?

​How do we find the consant?

​- Point (1,2)

​2/1=k(1)/1

2/1=k

k=2​​

​Use the formula k=y/x to see if points (2,4) and (3,6) equal the same value for k.

​

​k=4/2 k=2

​k=6/3 k=2

​

​*Because k the same value at each point the graph is proportional.

Multiple Choice

How do we know this graph is proportional?

• k is the same value at each point

• The line intersects with the origin

• The line is straight

• All of the above

Fill in the Blanks

What is the constant k For this graph?

k=y/x

​Great Job!