Question

Really need help! Been trying to solve for a while.

1. Solve the system by using a table. 3y=4x+7 , -4x-4y=28. These are the possible solutions:(–4, –3),(–3, –4), (4, 3),(3, 4).

2.Solve by graphing. -3x-y=-10, 4x-4y=8. possible solutions:(-1,3), (3-1), (1,3), (3,1)

Answer 1

Also help with this problem : The spreadsheet shows the monthly revenue and expenses for a new business. Use the models to predict the month in which revenue will equal expenses. Possible answers:
October
September
August
May

Answer 2

help with any of them would be really appreciated (:

Answer 3

I think September is your answer for the second problem

Answer 4

your estimate is as good as any haha. I have no clue so even an educated guess is better than nothing

Answer 5

I honestly just suck horribly at solving systems of any sort x.x

Answer 6

I answered it that way by reproducing the pattern of increase in the revenue and expense columns--that is, by adding differences in a row. Does that sound legitimate?

Answer 7

Sounds alright to me haha

Answer 8

I think I can solve the system, but I'm not sure what is meant by table. Is it all right if you use substitution and elimination?

Answer 9

I would just really like some help with the 1st two because there are lot's of other questions like them, including on upcoming tests. That I really don't want to get wrong :/

Answer 10

Yeah that's what I was trying to do. I however looked up solving solutions on google and it showed a way to do it where you used a graph to figure out where the two lines crossed. It didn't make sense with my equation though.

Answer 11

\[-3x-y=-10\]\[ 4x-4y=8\]
first equation is the same as \(y=-3x+10\) so you can replace \(y\) in the second equation by \(-3x+10\) with judicious use of parentheses
you get
\[4x-4(-3x+10)=8\] and now you have one equation and one variable to solve

Answer 12

you get
\[4x+12x-40=8\]
\[16x-40=8\]
\[16x=48\]
\[x=48\div 16=3\]

Answer 13

As long as it end up with an x and a y and they are one of the options above I really don't understand why it matters so much how we got it haha. I suppose in some cases it really matters but..

Thanks satellite that makes sense. I'll try writing it out.

Answer 14

hope the steps are claere

Answer 15

yeah I think so, so what next?

Answer 16

now that you have \(x=3\) you can replace \(x\) by 3 in either equation to solve for \(y\)

Answer 17

for example we know
\(y=-3x+10\) and we know \(x=3\) making \(y=-3\times 3+10=-9+10=1\)

Answer 18

okay haha, I think I get that too x.x

Answer 19

solving by graphing is too much work, and besides, if the answer is \((-\frac{1}{7}, \frac{5}{7})\) for example you will never know it from the graph

Answer 20

I know I really hate it too :/ Then again I hate all math. But it's what they are making us do so .

Answer 21

yes, sometimes math (especially this kind) is hateful
that is why they invented computers
for example, here is the answer to the first one
http://www.wolframalpha.com/input/?i=+3y%3D4x%2B7+%2C+-4x-4y%3D28

Answer 22

oh wow that's really cool! Thanks alot.