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#1 2014-07-28 04:03:40

Gabrielle
Guest

Solving Systems of Equations Using Substitution Method and Elimination

Ive done these multiple times and I feel like giving up. I don't understand what my teacher is saying.

#8

y=(1/2)x-3

y=(3/2)x-1

y=(1/2x-3

(3/2)x-1=(1/2)x-3

           +1           +1

(3/2)x=(1/2)x-2

(4/2)x= -2

4x = -2

x= -2

y=(3/2)x-1

y=(3/2)-2-1

y=-3-1

y= -4

(-2,-4)



#12

4x + 3y= -15

y=x+2

4x+3(x+2)=-15

4x+3x+6=-15

7x=-21

x=-3

y=x+2

y=-3+2

y=-1

(-3,-1)



#16

y=-2x+1

y=x-5

y=3x+6

x=2

y-6=3x

y=-3x

(2,-3)






and this is what my teacher said...
#8 - Tell me what you did to get from the first step to the second. 

(3/2)x=(1/2)x-2

(4/2)x= -2

#12 - The work must show elimination. You have used substitution. Try again.

#16 - I don't see your elimination work.  Please look at the example that I provided in my last post to help you show your work for #12 and #16.






she gave me this example but im not sure how to put my problems like this






Your work doesn't flow very well.  You do not need to fix this one, but take a look at the proper way to show your work.

x + 2y = -4       Already in standard form.

4y = 3x + 12     Write in standard form.

--------

x + 2y = -4

-3x + 4y = 12       Now determine what you need to multiply the equations by.

--------

3(x + 2y = -4)

3x + 6y = -12

-3x + 4y = 12     Now add the equations together to eliminate the x's.

------------------

10y = 0

y = 0       Substitute 0 for y in one of the original equations.

-----------------

x + 2y = -4

x + 2(0) = -4

x = -4

(-4, 0)

#2 2014-07-28 04:05:39

Agnishom
Real Member
From: The Complex Plane
Registered: 2011-01-29
Posts: 18,841
Website

Re: Solving Systems of Equations Using Substitution Method and Elimination

Hi;

What sort of help can We provide you?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
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#3 2014-07-28 04:09:22

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,562

Re: Solving Systems of Equations Using Substitution Method and Elimination

Hi;

The question has already been answered by bob bundy.

http://www.mathisfunforum.com/viewtopic … 82#p326582

Please go there.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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