I do not understand how to slove systems of equations by elimination Example: -4x-2y=-12 and then this one goes under it 4x+8y=-24  i have my math homework to do and i dont not understand it...

I do not understand how to slove systems of equations by elimination

Example:

-4x-2y=-12 and then this one goes under it

4x+8y=-24

 

i have my math homework to do and i dont not understand it neither does my mom i do not have my phone so i can not call anybody for help

Asked on by falynmarie

5 Answers | Add Yours

cburr's profile pic

cburr | Middle School Teacher | (Level 2) Associate Educator

Posted on

Falynmarie is right that you would often want to change one of the equations to positive or negative by multiplying both sides by -1. However, with this one, I think you are fine as you are.

-4x - 2y = -12

4x + 8y = -24

______________

0 + 6y = -36

or 6y = -36

Then divide both sides by 6 to isolate the y:

6y = -36

y = -6

Now substitute the -6 to find x:

-4x - 2 (-6) = -12

-4x - (-12) = -12

-4x + 12 = -12

Subtract 12 from both sides:

-4x = -24

x = 6

Let's try it with the other equation too:

4x + 8 (-6) = -24

4x - 48 = -24

add 48 to both sides:

4x = 24

x = 6

So, the end result is that x = 6 and y = -6

 

givingiswinning's profile pic

givingiswinning | Student, Grade 10 | (Level 1) Valedictorian

Posted on

-4x - 2y = -12

4x + 8y = -24

0 + 6y = -36

6y = -36

y = -6

4x + 8(-6) = -24

4x + -48 = -24

4x = -24 + 48

4x = 24

x = 6

x=6 y = -6

atyourservice's profile pic

atyourservice | Student, Grade 11 | (Level 3) Valedictorian

Posted on

-4x - 2y = -12

4x + 8y = -24

0 + 6y = -36

6y = -36

divide by 6 to get y

y = -6

now plug in this number as y in any one of the equations:

4x + 8(-6) = -24

4x + -48 = -24

4x = -24 + 48

4x = 24

divide by 4 to get x

x = 6

x=6 y = -6

revolution's profile pic

revolution | College Teacher | (Level 1) Valedictorian

Posted on

-4x-2y=-12- eqn 1

4x+8y=-24 - eqn 2

Next, add eqn 2 to eqn 1

-4x+4x-2y+8y=-12-24

6y=-36

y=-6

Next, sub. y=-6 to eqn 2

4x+8(-6)=-24

4x-48=-24

4x=-24+48

4x=24

x=6

Final answer is x=6, y=-6

falynmarie's profile pic

falynmarie | Student, Grade 9 | eNotes Newbie

Posted on

you have to change one of the problems from postive to negitive or negitive to postine to elimate the x or the y (make it zero) ans when you are done doing you should be able to divide and get eaither what x is or what y is and when you got that you can go and plug the x or the y in to one of the problens and get the other point

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