Wednesday,
th
September 25
Please complete the warm up 
1.
2.
Solve by elimination
2x – 4y = 12
-2x + 6y = 2
5x + 8y =24
3x + 8y = 12
Homework
Answers
The answer to a system of linear
equations is always a(n)
_________________.
Solve by substitution
4x + y = 12
5x – 6y = 15
What variable would be best to solve
for?
y=8
Is a ______________line
Solve by Graphing
Y = -3x + 6
X=5y + 12
What would be the first thing I need to
do to solve?
X=8
Is a ______________line
How would I eliminate a system
like this?
x + 2y = 11
–3x + y = –5
In some cases, you will first need to
multiply one or both of the equations by
a number so that one variable has
opposite coefficients.
x + 2y = 11
–3x + y = –5
•What could I multiply one of the equations by to
ELIMINATE the x’s?
•What could I multiply one of the equations by to
ELIMINATE the y’s?
Practicing the first step!
Practice
Makes
Perfect!!!
Decide what equation(s) to multiply
AND what number to multiply by so
that you can ELIMINATE one of your
variables.
(Don’t Solve)
1. 2x – 5y = 10
3x + 10y = 8
2. -4x – 6y = 8
x + 7y = 12
3. –x + 6y = 3
3x - 8y = 4
–5x + 2y = 32
2x + 3y = 10
Step 1 2(–5x + 2y = 32)
5(2x + 3y = 10)
–10x + 4y = 64
+(10x + 15y = 50)
Step 2
19y = 114
y=6
Multiply the first equation
by 2 and the second
equation by 5 to get
opposite x-coefficients
Add the new equations.
Simplify and solve for y.
Step 3 2x + 3y = 10
2x + 3(6) = 10
2x + 18 = 10
–18 –18
Step 4
2x = –8
x = –4
(–4, 6)
Write one of the original
equations.
Substitute 6 for y.
Subtract 18 from both sides.
Simplify and solve for x.
Write the solution as an
ordered pair.
Solve the system by elimination.
2x + 5y = 26
–3x – 4y = –25
Step 1 3(2x + 5y = 26)
+(2)(–3x – 4y = –25)
Multiply the first equation
by 3 and the second
equation by 2 to get
opposite x-coefficients
6x + 15y = 78
+(–6x – 8y = –50) Add the new equations.
Step 2
0 + 7y = 28
Simplify and solve for y.
y =4
Step 3
2x + 5y = 26
2x + 5(4) = 26
2x + 20 = 26
–20 –20
2X
= 6
x=3
Step 4
(3, 4)
Write one of the
original equations.
Substitute 4 for y.
Subtract 20 from both
sides.
Simplify and solve for x.
Write the solution as an
ordered pair.
#3 You Try!
9x + 6y = 12
8x + 3y = 13
#4 You Try!
9x + 2y = 2
4x + y = 1
#5 You Try!
2x – 3y = 4
-4x + 5y = -8