Download Solving 2 Step Equations

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When you do something
to one side of an equation,
x 1  9
1
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you have to do exactly
the same thing
to the other side.
x 1  9
1 1
x 8
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the addition or
subtraction operation first,
by using inverse operations.
2) Undo the multiplication or
division operation second,
by using inverse operations.
1) Undo
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Remember The
Party?
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Who’s the friend and who’s the
boyfriend or girlfriend?
3x + 4 = 16
4 is the friend 3 is the boyfriend
Undo add 4 by
or girlfriend
subtracting 4
Undo multiply 3 by
dividing by 3
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REMEMBER TO CROSS THINGS OUT SO
YOU KNOW YOU ARE DOING IT RIGHT
3x + 4 = 16
-4 -4
3x = 12
3
3
x=4
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1) GOAL: Get the variable alone on one side
of the equation.
2) You always perform the same operation to
both sides of an equation.
3) To undo an operation you perform its
opposite operation to both sides of the
equation.
4) Undo addition or subtraction before you
undo multiplication or division.
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2x + 4 = 10
-4 -4
2x = __
__
6
2
2
x
=3
Get the variable alone.
Subtract 4 from both sides.
+4 and -4 cancel out
Divide both sides by 2
2 divided by 2 cancel to 1
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3m - 10 = 17
+ 10 +10
3m
__
3
m
= __
27
3
=9
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x
3
3
x
3
x
(3
x
–4=8
+4 +4
Get the variable alone.
= 12
+ 4 and -4 cancel out.
Add 4 to both sides.
) = 3 12 Multiply both sides by 3.
= 36
3 divided by 3 cancel to 1
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x
2
2
x
2
x
(2
x
+ 6 = 14
-6 -6
=8
) =2 8
= 16
16
2
+ 6 = 14
8 + 6 = 14
14 = 14
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What Operation Do You Do?
1) 3x + 8 = 24
FIRST
Subtract 8
SECOND
Divide by 3
2) 5x - 10 = 19
Add 10
Divide by 5
3) x - 4 = 20
2
Add 4
Multiply by 2
4) - 30 = -5x + 5 Subtract 5
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Divide by -5
1) 2x  5  19
5  5
2x  24
2
2
x  12
x
2) 15   6
3
15
 15
x
3 3  9 3
x  27
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Textbook:
Page 123
Examples 8 - 19
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3) 8x  1  25
1  1
8x  24
8 8
x3
x
4)  4  3
5
4  4
x
 5 5  7  5 
x  35
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Think about what you need to
do to isolate the variable.
Get rid of addition or subtraction
first. Second get rid of
multiplication or division.
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The
End!
Take out your study guide!
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#11
1) Undo the addition or subtraction
operation first, by using inverse
operations.
2) Undo the multiplication or
division second, by using inverse
operations.
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#12
2 Step Subtract/Multiply Equation
3m - 10 = 17
+10 +10
__
3m
3
m
__
= 27
3
=9
3(9) – 10 =17
27 – 10 =17
17 =17
Get the variable alone.
Add 10 to both sides.
+10 and -10 cancel out
Divide both sides by 3
3 divided by 3 cancel to 1
Show your check.
Finish your check.
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#13
x
2
x
2
x
2( 2
x
+ 6 = 14
-6 -6
=8
Get the variable alone.
Subtract 6 from both sides.
+ 6 and -6 cancel out.
) = 2 8 Multiply both sides by 2.
= 16
16
+
6
=
14
2
8 + 6 = 14
14 = 14
2 divided by 2 cancels out
Show your check.
Finish your check.
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TEACHER NOTE: Use the
following slides the next day
when correcting homework.
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HOMEWORK
EXPLANATION
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An Equation is like a balance
scale. Everything must be equal
on both sides.
=
20
2x +5
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What you do to one side of an
equation, you must do to the
other side to keep it balanced!
=
20
-5
2x +5
-5
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What you do to one side of an
equation, you must do to the
other side to keep it balanced!
=
15
__
2
2x
__
2
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What you do to one side of an
equation, you must do to the
other side to keep it balanced!
=
7.5
x
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Try to solve this subtraction equation
How do you get n all by itself?
=
18
+3
n -3
+3
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Try to solve this subtraction equation
How do you get n all by itself?
=
21
n
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Show your check by substituting your
answer back into the original
equation.
=
18
21
n -3
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Try to solve this division equation
How do you get x all by itself?
x •3
3
=
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15 •3
Try to solve this division equation
How do you get x all by itself?
x
=
45
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SHOW YOUR CHECK!
45
x
3
=
15
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