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View Full Version : Algebra: solve by elimination


TysonBrown
Jan 20, 2009, 03:50 PM
I don't know what to get rid of!

-2x+3y=14
x-4y=-12



Help me!

ROLCAM
Jan 20, 2009, 05:09 PM
-2x+3y=14
x-4y=-12
_______________________
-2x+3y=14
2x-8y = -24
_____________________
eliminate the x's you get:

+3y = 14
-8y = -24

so
-5y = -10

y = 2

x-4y=-12
x = 4y-12
x=8 -12
x = -4

x = -4 and y = 2

sarnian
Jan 20, 2009, 07:17 PM
Rolcam : the student should be helped with an explanation to understand the question and procedure, and answer it himself/herself.

My advice to him/her would be :

Select either x or y, and substitute the value of it in the other term.
The easiest way here seems using x for that.

a) -2x+3y=14
b) x-4y=-12

We know the value of -2x as in term a) is stated : -2x + 4y = 12 , so -2x =...

We know the value of x as in term b) is stated : x - 4y = -12 , so x =...

Divide the value of -2x in term a) with -2 (divide everything with -2), and you get : x =...

Now substitute the value of x from term a) into term b) , and solve y !

This board is called "Homework Help", and not "Do their homework !!!"

shebester
Jan 20, 2009, 07:24 PM
Rolcam you are amazing thanks