SOLUTION: Use Linear Combinations to solve the Linear System 2-7x=9y 2y-4x=6 I dont get how you use linear combinations to solve this. My book doesn't explain things into detail and

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Question 429582: Use Linear Combinations to solve the Linear System
2-7x=9y
2y-4x=6
I dont get how you use linear combinations to solve this. My book doesn't explain things into detail and my teacher doesn't either. Thanks!

Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Use Linear Combinations to solve the Linear System
2-7x=9y
2y-4x=6
-----------
Not sure what you mean by combinations. I'll use elimination, which in a way combines the 2 eqns.
2-7x=9y
2y-4x=6
--------
9y+7x = 2 eqn 1
1y-2x = 3 eqn 2 divided by 2
----------
9y + 7x = 2 eqn 1
9y -18x = 27 eqn 2 divided by 2 then x9
---------- Subtract
0y +25x = -25
x = -1
---------
1y-2x = 3 Sub for x
y + 2 = 3
y = 1
That's it.

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