Transcript notes

Solving a system of equations by
adding or subtracting
When using the
2x + 3y = 11
adding or subtracting
method, one of the -2x + 5y = 13
variable
8y = 24
combinations can
8 8
completely eliminate
y=3
themselves if you
were to combine the
2 equations together
In this example, the
X’s can
Eliminate themselves
What we know now
is that the answer
will be (?, 3)
To find the value
of x you
Use either
equation from
The question and
substitute
In to find your
answer
2x + 3(3) = 11 The
2x + 9 = 11
-9 -9 Answer
2x = 2
Is
2 2
x = 1 (1, 3)
When using the
adding or subtracting
method, one of the
variable
combinations can
completely eliminate
themselves if you
were to combine the
2 equations together
4x + 3y = 2
-5x
3y == -2
2
5x +– 3y
-1x = 4
-1 -1
x = -4
In this example, the Y’s
can eliminate themselves
If we do 1 thing first
What we know now
is that the answer
will be (-4, ?)
To find the value
of y you
Use either
equation from
The question and
substitute
In to find your
answer
4(-4) + 3y = 2 The
-16 + 3y = 2
+16
+16 Answer
3y = 18 Is
3
3
y = 6 (-4, 6)
In this example, we
need for both
equations to be in
the same form. I am
going to put the
bottom equation
into standard form to
solve.
-3x + 4y = 14
What we know now
is that the answer
will be (2, ?)
8x – 4y = -4
-3x=+3x
4y+=14
14
4y
5x = 10
5
5
x=2
To find the value
of y you
Use either
equation from
The question and
substitute
In to find your
answer
8(2) - 4y = -4 The
16 - 4y = -4
-16
-16 Answer
-4y = -20 Is
-4 -4
y = 5 (2, 5)
Pg. 447
4 – 20 even