SOLUTION: Could someone show me how to work a few problems on the substitution method? 1) x + y = 15 4x + 3y = 38 2) -3x + y = -4 x - y = 0 I have the directions on

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Question 145330: Could someone show me how to work a few problems on the substitution method?
1) x + y = 15
4x + 3y = 38

2) -3x + y = -4
x - y = 0
I have the directions on how to work these,but I'm confused on how to write them down onto the paper.If you wouldn't mind showing me,that would help me so much to understand what I'm doing so when I have to take a test in the future.Thank you so much in advance Elle J
Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!


Jump to problem # 2
# 1

Start with the given system of equations:





Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to solve for y.




So let's isolate y in the first equation

Start with the first equation


Subtract from both sides


Rearrange the equation



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

Since , we can now replace each in the second equation with to solve for



Plug in into the first equation. In other words, replace each with . Notice we've eliminated the variables. So we now have a simple equation with one unknown.



Distribute to


Multiply


Combine like terms on the left side


Subtract 45 from both sides


Combine like terms on the right side





-----------------First Answer------------------------------


So the first part of our answer is:









Since we know that we can plug it into the equation (remember we previously solved for in the first equation).



Start with the equation where was previously isolated.


Plug in


Multiply


Combine like terms



-----------------Second Answer------------------------------


So the second part of our answer is:









-----------------Summary------------------------------

So our answers are:

and

which form the point






Jump to problem # 1
# 2

Start with the given system of equations:





Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to solve for y.




So let's isolate y in the first equation

Start with the first equation


Add to both sides


Rearrange the equation


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

Since , we can now replace each in the second equation with to solve for



Plug in into the first equation. In other words, replace each with . Notice we've eliminated the variables. So we now have a simple equation with one unknown.



Distribute the negative


Combine like terms on the left side


Subtract 4 from both sides


Combine like terms on the right side


Divide both sides by -2 to isolate x



Divide





-----------------First Answer------------------------------


So the first part of our answer is:









Since we know that we can plug it into the equation (remember we previously solved for in the first equation).



Start with the equation where was previously isolated.


Plug in


Multiply


Combine like terms



-----------------Second Answer------------------------------


So the second part of our answer is:









-----------------Summary------------------------------

So our answers are:

and

which form the point

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