Ask Experts Questions for FREE Help !
Ask
    Ninjagirl14's Avatar
    Ninjagirl14 Posts: 7, Reputation: 1
    New Member
     
    #1

    Mar 18, 2009, 02:39 PM
    Algebra substitution and elimination
    OK so I need help with my homework I don't get how to do it
    :(
    4x+3y=1
    x=1-y

    so far I have

    4(1-y)+3y=1
    4-4y+3y=1
    -1/-1 =1/-1
    x=-1
    1--1
    y=-2 (-1,-2)

    do I have it right or is it wrong and if its wrong show me what step I did wrong and thank you
    :D
    JTnumber3's Avatar
    JTnumber3 Posts: 7, Reputation: 1
    New Member
     
    #2

    Mar 18, 2009, 03:35 PM

    Hehe, Lets see if I can help you. This subject is one of my strong ones ;)

    4x + 3y = 1 (If x = 1 - y ) then,

    First Step: 4( 1 - y ) + 3y = 1.

    Second Step: 4 - 4y + 3y = 1.

    Third Step (group all x's to one side, and all non x's to another): -4y + 3y = -4 + 1.

    Fourth Step: -y = -3, but you want to find positive y not negative y. So it ends up being y = 3.

    Fifth Step: Plug in the answer you got to find why in the original problem to find x.

    Sixth Step: 4x + 3(3) = 1.

    Seventh Step: 4x + 9 = 1. Then, we group non variables on one side and the numbers w/ variables on the other.

    Eighth Step: 4x = -9 + 1. Therefore, 4x = -8.

    So, x = -8/4

    Answers are: y = 3 , x = -2.

    P.S. - Sorry for all the steps, I needed to show you the EASIEST WAY to find what x and y are and in the most precise way. Hope this helped!
    Ninjagirl14's Avatar
    Ninjagirl14 Posts: 7, Reputation: 1
    New Member
     
    #3

    Mar 18, 2009, 04:11 PM
    thanks it helped no I have a different problem its
    2x-y=6
    -x+y=-1:confused:
    brittanybaby123's Avatar
    brittanybaby123 Posts: 1, Reputation: 1
    New Member
     
    #4

    Mar 18, 2009, 04:14 PM
    Quote Originally Posted by Ninjagirl14 View Post
    ok so i need help with my homework i dont get how to do it
    :(
    4x+3y=1
    x=1-y

    so far i have

    4(1-y)+3y=1
    4-4y+3y=1
    -1/-1 =1/-1
    x=-1
    1--1
    y=-2 (-1,-2)

    do i have it right or is it wrong and if its wrong show me what step i did wrong and thank you
    :D
    ::cool:

    Its correct good job
    JTnumber3's Avatar
    JTnumber3 Posts: 7, Reputation: 1
    New Member
     
    #5

    Mar 18, 2009, 04:45 PM
    Make sure to write out the whole problem if you have not, it's a little confusing if you have only one or two problems.

    So, what you said was 2x - y = 6. And -x + y = -1.

    It would make most sense that in the ( -x + y = -1 ), -x would equal 5 and y would equal 4. Therefore, in the (2x - y = 6), x would equal 5 and negative y would equal 4.

    Checking: 2(5) - 4 = 6 --> 10 - 4 = 6. YES.

    Checking: -x + y = -1 --> -5 + 4 = -1. YES.





    Here's a helpful tip: In algebra, If you want your answer of -x to be positive, than you would write (1) -x = -5, since the two negatives cancell each other out to make it positive.

    If you want the answer of x to be negative, than you would write (1) x = -5 , (2) -x = 5.

    It is WRONG to say that negative x equals negative 5 -->(-x = -5). This turns out to be positive x equals positive 5 (x = 5).
    JTnumber3's Avatar
    JTnumber3 Posts: 7, Reputation: 1
    New Member
     
    #6

    Mar 18, 2009, 04:50 PM

    Another Solution is: if you wrote

    2x - y = 6
    - x + y = -1

    then it would be

    x = 5. Than Plug in the answer for x in the 2x - y = 6 problem. So 2(5) - y = 6. Therefore, -y = -10 + 6. Last, -y = -4, so negatives cancell and it will be y = 4.

    I think you needed the ANSWER TO THIS ONE. FORGET ABOUT THE OTHER ONE That's FOR A MORE COMPLICATED PROB. ;)

    HOPE THIS HELPED. BTW the first problem was wrong but I corrected it for you.
    Ninjagirl14's Avatar
    Ninjagirl14 Posts: 7, Reputation: 1
    New Member
     
    #7

    Mar 18, 2009, 06:47 PM

    thanks =D
    maybaby978's Avatar
    maybaby978 Posts: 1, Reputation: 1
    New Member
     
    #8

    Mar 26, 2009, 05:32 PM

    x+y=-9
    5x-2y=32

    how to use elimantion to solve this

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Algebra Ii (elimination & Substitution) [ 8 Answers ]

solve by elemination {x + y = 10 x - y = 2 solve by substitution y = x +1 2x + y = 7

Elimination and substitution math [ 6 Answers ]

how do I do this problem? 4x-3y=12 x+2y=14

Elimination or substitution [ 5 Answers ]

I have tried to see both ways of eliminationa and substitution and I am having a hard time with this problem. I have the answer, I want to see how to GET the answer. I need to see work and steps please, and thank you. By the way, the answer is (4,2) 7x-2y=24 5x+4y=28

Elimination or Substitution and how do I do it? [ 1 Answers ]

^=exponent y^2=25 x^2-2x=4x+16 :eek:

Substitution or Elimination [ 1 Answers ]

y=-2x-3 4x+3y=3 someone help me with my homework!!


View more questions Search