Algebra y=mx+b question

[Zena2017]

Hi, everyone, I have been stuck on this question for a week and I don't even know if I started correctly or not?

Below is the question and under the question in bold is my answer but I can't seem to get the full formula correct. Please help me, I also posted the second question under which I'm also needing some aid in.

Frod Motors	Toyrolla Motors
Money Down= $320 Cost per Month= $350	Money Down= $2000 Cost per Month= $210

My first Question:
Write a linear equation of the form y₁=mx+b for Frod Motors. Graph this equation on the xy-plane and label it as y₁. (You may use Excel to graph or you can save the graph paper (click here to download) to your desktop and use the 'draw' tools in Word to plot your lines. It would make sense to have your X values increase by 2, perhaps using the set [0,20]. Be sure to include a large enough set of y-values (something like [0,8000] would be suitable since leasing costs in the thousands of dollars. Increasing values by 500 would make sense. Graphsketch.com is resource which you may find helpful when constructing your graph. Also, be sure to include a title on the graph and labels on the x- and y-axes.

This is what i came out with:
Ford Motors- Money Down 320 Cost per Month 350
y = mx +b
slope or m = 350 per month
b = 320 (fixed value)
y = 350x
Toyrolla Motors- Money Down 2000 Cost per month 210
y=mx+b
slope or m= 210 per month
b= 2000 (fixed value)
y= 210x



My second Question is below:
Write a linear equation of the form y₂=mx+b for Toyrolla Motors. Graph this equation on the same graph. You will now have two lines on the same graph. These should intersect.

 

[mmm4444bot]

Frod Motors	Toyrolla Motors
Money Down= $320 Cost per Month= $350	Money Down= $2000 Cost per Month= $210

Write a linear equation of the form y₁=mx+b for Frod Motors. Graph this equation on the xy-plane and label it as y₁.

Write a linear equation of the form y₂=mx+b for Toyrolla Motors. Graph this equation on the same graph [and label it as y_2].

y = mx +b

slope or m = 350 per month

b = 320 (fixed value)

y = 350x That variable ought to be y₁

You correctly identified the constants m and b, but you did not add mx and b, in your equation for y₁.

As you can see, the complete Slope-Intercept form of a linear equation is:

y = mx + b

You wrote only y = mx, so add on the value of b at the end.

Toyrolla Motors- Money Down 2000 Cost per month 210

y = mx + b

slope or m= 210 per month

b= 2000 (fixed value)

y = 210x That variable ought to be y₂

This is y = mx, instead of y = mx + b.

Again, add on the value of b, at the end.

---

Here's a couple of other comments.

1) With word problems, it's good practice to identify in writing the meaning of variables (x and y); include this with your work.

y₁ = leasing cost at Frod Motors

y₂ = leasing cost at Troyolla Motors

x = number of months since lease began

Also, when you label your graph, you could write "Lease Cost" to the left of the y-axis and "Months" underneath the x-axis.

2) It's true that b represents a fixed cost (the down payment), but it is also called the y-intercept (i.e., the point where a line crosses, or touches, the y-axis) because when x=0 the y-coordinate is simply b.

In other words, when x=0 (the first day of the lease), the cost is b because, in the equation, m*x becomes zero.

For example, the coordinates of the y-intercept for the Frod Motors line are (0, 320)

This point shows the lease cost as $320, on the first day of the lease (the number of months since the lease began is x=0). :cool: