Transcript Solving a system of equations by multiplying

Solving a system of equations by
multiplying
When using the
multiplication
method, one of the
equations will need
to be multiplied by
something to make
one of the variable
combinations
eliminate themselves
6x + 5y = 19
-3(2x + 3y = 5 )
6x + 5y = 19
-6x - 9y = -15
In this example, the X’s
can eliminate
themselves if we
multiply the bottom
row by -3
What we know now
is that the answer
will be (?, -1)
To find the value
of x you
Use either
equation from
The question and
substitute
In to find your
answer
-4y = 4
-4 -4
y = -1
6x + 5(-1) = 19 The
6x -5 = 19
+5 +5 Answer
6x = 24 Is
6 6
x = 4 (4, -1)
-50 ( 0.2x – 1.5y = -1)
In this example, the 10 ( x – 4.5y = 1)
X’s can eliminate
-10x + 75y = 50
themselves if we
multiply the top row
10x
–
45y
=
10
by -50 and the
bottom row by 10
This way you will
have no decimals
and the X’s will
eliminate
themselves at the
same time
What we know now
is that the answer
will be (?, 2)
The
Answer
Is
(10, 2)
30y = 60
30 30
y=2
10x – 45(2) = 10
10x -90 = 10
+90 +90
10x = 100
10 10
x = 10
Pg. 454 – 455
4 – 28 even
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