Question

Hello, I need help with an equation
i did it, but it looks like it needs revision
• A teacher is looking for the best option in purchasing school supplies for a classroom. Company A is offering a discount for every dollar amount spent; Company B is offering a higher discount than Company A, but the discount is applicable only for every dollar amount spent above $20. Determine which company will offer a better price based upon the dollar amount the teacher spends on school supplies.

Answer 1

do you have a formula for determining the cost of each company? If you don't, develop a formula for each company, and then I can help you from there

Answer 2

yes i do
there are three separate formulas
y=0.8x
y=0.7x+6 and y=x

Answer 3

I am having trouble with the excel graph, and i don't know if something is just not adding up

Answer 4

I'm not sure what those equations correspond to

Answer 5

well, the discounts are 20% from Company A based on any amount purchased, and 30% from Company B for supplies purchased above $20.

Answer 6

ok, so when for the second one, when x is 20, y is twenty, and afterwards y = (x -20) * .7

Answer 7

sorry, y = (x - 20) * .7 + 20

Answer 8

yes
but how do I put it in a graph? how do I find my points for those 3 equations? I attached an excel graph, but something isn't accurate

Answer 9

sorry, i can't open up the excel graph. but to solve the problem, you solve for the two equations i posted above

Answer 10

did you use scatter plot instead of line graph?

Answer 11

go to where you change chart type, and choose the segmented line, instead of the smooth curve under scatter plot

Answer 12

in the scatter chart?

Answer 13

Can I put any numbers to solve the equation, or how would I solve this equations above?

Answer 14

you see how two of the equations intersect on the graph?

Answer 15

yes, at 60, but at the bottom, i have a bump

Answer 16

these are the points that I use, 0, 20,40, 60,80

Answer 17

at x = 20, it will be discontinuous. it's supposed to be

Answer 18

x1 y1 x2 y2
0 0 0 0
20 16 20 20
40 32 30 27
60 48 40 34
80 64 60 48

Answer 19

i think something is wrong with the points that I'm using

Answer 20

use the equations i gave then

Answer 21

Are they the same as y=0.8x and 0.7x+6? Or can you regive me your equations if they are different?

Answer 22

why is it six and not 34? from 0 - 20, the equations should be y = .8 * x and y = x, after 20, it should be y = .8 x and y = .7 * x + 34

Answer 23

you know what, nevermind, the equation is right, i added 14 + 20 instead of subtracted

Answer 24

so your equations are correct

Answer 25

Whew, a relief since I have been working on them since yesterday. But my question is, what points do I use to plot the graph? How do I solve the equations?

Answer 26

I'm like math illiterate, which is probably why you're wondering why I'm having a hard time with these equations.

Answer 27

your points are correct, it shows exactly where the two graphs are equal. the only problem is, you chose to have the graph smooth the lines, instead of jagged. make them jagged

Answer 28

you see where it's curvy? it should just be an angle

Answer 29

how do I make them jagged? and do I need to do a point for the equation y=x

Answer 30

no, read up top, you need to change the graph type

Answer 31

look in excel where it has the types, where one is curved, and the other is jaggedy

Answer 32

So you can see my graph in front of you, does it make sense to you with both companies?

Answer 33

yes, it's fine, except that it's curved, and not jaggedy

Answer 34

in my excel, if i right click on the graph, and go to CHANGE CHART TYPE, i have the option on the bottom of the window to change it to a jagged scatter plot. other than that, it's supposed to have them cross like that, and the one is supposed to slightly change direction

Answer 35

Ok and how do I simultaneously solve those 3 equations?

Answer 36

you don't simultaneously solve all three

Answer 37

only the two, after x > 20

Answer 38

ok and how do I solve those 2? I'm sorry if I sound clueless, but I just don't understand math

Answer 39

you see how you have them already solved for y? you just set the right side of the one to the right side of the other, as in .8x = .7x+6, and solve for x

Answer 40

ok let me try that

Answer 41

x=60?

Answer 42

Would I be able to attach the file for the word problem so you can see if I did it right?

Answer 43

no, you did that right, but your answer doesn't match your data

Answer 44

so how do I fix it?

Answer 45

wait, is that your x or your y?
your x is 60, and your y is 48?

Answer 46

yes

Answer 47

then you're done

Answer 48

So the equations with the graph are accurate?

Answer 49

This is what it asks for?

Answer 50

3. Solve the system of linear equations algebraically using either the substitution method or the elimination method to determine where the two cost options are equivalent, showing all work.

a. Explain each step used to solve the system of linear equations. Include the following in your explanation:

• The algebraic method used to solve the system of equations

• All mathematical operations used to solve the system of equations

• The solution of the system of equations

Answer 51

Which method did I use?

Answer 52

substitution

Answer 53

How did you come up with all three equations?

Answer 54

Are you there?