SOLUTION: My question is based around 'Solving Systems of Equations by the Substitution Method'. I understand the concept of plugging in the x or y value into the one or the other equati

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Question 1000000: My question is based around 'Solving Systems of Equations by the Substitution Method'.
I understand the concept of plugging in the x or y value into the one or the other equation but for some (very frustrating) reason whenever I follow these steps I don't come out with the right answer. I will list two below.

1. 4x-y=-1
2x+4y=13
I chose to take the top equation (4x-y=-1) and make that into -y=-4-1 and change that further by dividing by -y to get y=-4x+1. MY FIRST QUESTION is why did I have to change -1 to +1?
I then tried to plug y=-4x+1 into the 2x+4y=13 but I never get the right answer! Help?


2. x-3y=-11
6x-y=2
please help?
Found 2 solutions by mananth, MathTherapy:
Answer by mananth(16946)   (Show Source): You can put this solution on YOUR website!
4x-y=-1
subtract 4x from both sides
4x-4x-y = -1-4x
-y =-1-4x
divide by -1
y=4x+1
If you observe the original equation
when you take any term on the other side of the equation the sign changes from + to - OR - to +
2x+4y = 13
2x+4(4x+1) =13
2x+16x+4=13
18x=13-4 ( The sign of 4 has changed bcause I brought it on the right side)
18x=9
/18
x=9/18
x=1/2
plug x


2x+4y=13
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

My question is based around 'Solving Systems of Equations by the Substitution Method'.
I understand the concept of plugging in the x or y value into the one or the other equation but for some (very frustrating) reason whenever I follow these steps I don't come out with the right answer. I will list two below.

1. 4x-y=-1
2x+4y=13
I chose to take the top equation (4x-y=-1) and make that into -y=-4-1 and change that further by dividing by -y to get y=-4x+1. MY FIRST QUESTION is why did I have to change -1 to +1?
I then tried to plug y=-4x+1 into the 2x+4y=13 but I never get the right answer! Help?


2. x-3y=-11
6x-y=2
please help?
4x - y = - 1 -------- eq (i) 

2x + 4y = 13 -------- eq (ii)

For the 1st equation, all you have to do is add y to both sides to get:

4x = - 1 + y

Then add 1 to get: 4x + 1 = y 

Now we have: y = 4x + 1 ------- eq (i)

2x + 4y = 13 --------- eq (ii)

2x + 4(4x + 1) = 13 ------- Substituting 4x + 1 for y in eq (ii)

2x + 16x + 4 = 13

18x = 9

x = , or 



 -------- Substituting  for x in eq (i)

y = 2 + 1, or 



Follow the same steps and you should be able to do no. 2 

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