SOLUTION: I need to find the intersecting points of two equations: y=.15x and y=.2(x-20)and graph them. I have included my problem and what is expected. I'm lost. Ok this is what I got

Algebra ->  Matrices-and-determiminant -> SOLUTION: I need to find the intersecting points of two equations: y=.15x and y=.2(x-20)and graph them. I have included my problem and what is expected. I'm lost. Ok this is what I got       Log On


   

Question 346098: I need to find the intersecting points of two equations: y=.15x and y=.2(x-20)and graph them. I have included my problem and what is expected. I'm lost.
Ok this is what I got :
You would set the two equations equal to each other and solve for x
.15x=.2(x-20) using the Elimination Method
Reorder the terms:
0.15x = 0.2(-20 + x)
0.15x = (-20 * 0.2 + x * 0.2)
0.15x = (-4 + 0.2x)
Solving
0.15x = -4 + 0.2x
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-0.2x' to each side of the equation.
0.15x + -0.2x = -4 + 0.2x + -0.2x
Combine like terms: 0.15x + -0.2x = -0.05x
-0.05x = -4 + 0.2x + -0.2x
Combine like terms: 0.2x + -0.2x = 0.0
-0.05x = -4 + 0.0
-0.05x = -4
Divide each side by '-0.05'.
x = 80
Simplifying
x = 80
Now that X = 80, I plugged it into the equation y=0.15x and got this:
y=0.15x
y=0.15(80)
y= 12
Now this is the question to my problem and I do not know how to get the answer. I have to graph this and show the intersection.
a teacher is looking for the best option in purchasing school supplies for a classroom. Where Company A is offering a discount for every dollar amount spent on school supplies and where Company B is offering a higher discount than Company A, but the discount for Company B is only offered for every dollar amount spent above $20.00. I will determine and explain which company will offer a better price based upon the dollar amount the teacher spends on school supplies.
Option 1- Company A will offer her a 15% discount on the total amount spent in the store.
Option 2- Company B will offer her a 20% discount on the remaining amount after the first $20 is spent.
Depict the situation graphically, using appropriate graphing software such as Excel or an online graphing utility.
Include the following in your graph:
• A depiction of each cost option on the same graph
• Clear labels of the cost to the hypothetical customer for both options on the graph
• The intersection of the cost options (if one exists)
I'm so lost. I do not know how to graph this. Please help if you can.
Found 2 solutions by Fombitz, mananth:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
First your answer is correct.
Now plotting.
y=0.15x
When x=0, y=0
when x=100,y=15
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Plot the points and the line connecting them.
The x-axis is the amount of money you spend.
The y-axis is the discount you receive.
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The red line is the savings from the Company A plan.
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The Company B savings only begins at x=20.
So you have to spend at least $20 to receive any discount.
y=.2%28x-20%29
When x=20,+y=0
When x=100, y=0.2%28100-20%29=16
Plot those points and line.
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The blue line is the savings from the Company B plan.
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When does the Company B plan savings equal the Company A plan savings.
You already calculated that point.
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When you spend $80, you get a savings from both plans of $12.
Plot that point too.
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Once you pass that point ($80), Company B savings (blue line) are higher than Company A.
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If you spend less than $80, Company A savings (red line) are higher than Company B.

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
y=0.15x
(10,1.5)(20,3)(30,4.5)
y=0.2x-4
(20,0)(30,2)(40,4)
Your intersection values of (80,12) is correct.
for each equation
take 3 values of x and calculate y
plot the two graphs
graph%28300%2C300%2C-1%2C100%2C-1%2C15%2C0.15x%2C0.2x-4%29
you will get 2 graphs as above
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