Transcript By Stanley Brown & Rodney Lewis It is a extension of the elimination method is to multiply one or both equations in a system.

By
Stanley Brown
&
Rodney Lewis
It is a extension of the elimination method is to
multiply one or both equations in a system by
some number so that adding or subtracting
eliminates a variable.
Need to know how to do basic elimination
Example: 3x-2y=5
-3x+4y=6
http://www.coolmath.com/algebra/12-2x2-systems-ofequations/03-solving-by-elimination-addition-01.htm
 Need to know how to solve multi step equations using
multiplication and division
http://www.coolmath.com/algebra/06-solvingequations/index.html


3x+4y=-25 Multiply by 2
(+) 2x-3y=6 Multiply by -3
6x+8y=-50
-6x+9y=-18

Add the equations, The
inverses will cancel leaving
“Y” by itself

Divide by 17 to find the
value of your “Y”

Your “Y” will be -4
17y = -68
17 17
y=-4
Multiply so that the “X”
coefficients are Additive
inverses.

2x-3y=6
2X-3(-4)=6
2x+12=6
2x+12=6
-12 -12
2x=-6
2 2
X=-3
To find your X you
have to substitute Y
back into one of the
equations. Y=-4

Multiply -4 by -3

Subtract 12 from both
sides of the equations.

Divide each said by 2


X will equal -3
Your final solution
will be (-3,-4)
1st Choose one equation and solve for x or y
Solve for y in the 2nd equation.
Multiply by -2
-6x-4y=-20
Multiply by 3
(+) 6x-3y=27
2nd Eliminate
Cancels your x value
3rd solve
Divide
-6x-4y=-20
(+)6x-3y=27
-7y=7
7
Y=-1
4Th Substitute the value found in step 2 back into one of the equations and solve.
Your Y value was equal to -1
6x-3(-1) =27
Subtract 3 from each side
6x+3=27
-3 -3
Divide 6 from each side
6x=24
6
Your solution will be (4,-1)
x=4
2x-y=6
3x+4y=-2
6.
8x-3y=-11
2x-5y=27
2x+7y=1
x+5y=2
7.
4x-7y=10
3x+2y=-7
3.
4x+7y=6
6x+5y=20
8.
4.
x+y=3
2x-3y=16
12x-3y=-3
6x+y=1
9.
1.8x-0.3y=14.4
x-0.6y=2.8
1.
2.
5.
2x+y=5
3x-2y=4
10. 3x-½y=10
5x+¼y=8


Elimination with multiplication
http://www.coolmath.com/algebra/12-2x2-systemsof-equations/03-solving-by-elimination-addition02.htm
fun way to practice with regular equations
http://www.coolmath-games.com/0arithmeticgame/index.html
Know enough? Try the test
 http://www.glencoe.com/sec/math/studytools/cgibin/msgQuiz.php4?isbn=0-07-8603900&chapter=7&lesson=4&headerFile=6&state=na
1.
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10.
(5,-1)
(4,-1)
(5,-2)
(5,-2)
(2,1)
(-4,-7)
(-1,-2)
(0,1)
(10,12)
(2,-8)