Problem of the Day
Solve the following system algebraically, using substitution:
y= -
1
x
2
–7
2x – 6y = 12
Solving Algebraically
I sure do love
by Elimination
that trusty
Look for a pair
of matching
opposites
substitution!
x + 3y = 8
+ 6x – 3y = 27
7x
7
But
sometimes
there’s an
easier way!
= 35
7
x=5
(5, 1)
x + 3y = 8
5 + 3y = 8
3y = 3
y=1
Problem of the Day
y= -
1
x
2
–7
2x – 6y = 12
What the
deuce!?
Mwahahahaha!
Try shoveling
a sidewalk
with that thing
buddy!
Anyway, where were we?
If you don’t have matching opposites, you can make them match.
4( 2x + y = 3 )
7x – 4y = 18
Find an LCM
to distribute
8x + 4y = 12
7x – 4y = 18
Steps to Solving by Elimination
Look for equal opposites or a pair
that’s easy to manipulate
Distribute the coefficient you need
across one or both equations to make
equal opposites
Add equations together and cancel pair
Solve for one variable
Plug answer back in to find other
variable
Practice
3x + 4y = 1
2x + 4y = 6
3x + 2y = -1
4x – 5y = -32
Solving Equations Algebraically
Using Elimination
__________________________________________________
x + 3y = 8
6x – 3y = 27
t have matching opposites, you can make them match: ___________________
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