Download Solving Two- Step Equations

Halloween Warm-Up
• Paul has two dozen Halloween cookies.
He will eat three cookies on Sunday. On
every day that follows, he will eat a
number of cookies that is one greater than
the day before. On what day will he find
that he doesn’t have enough cookies to
follow this procedure?
Answer
• Thursday
• Sun -3 Mon- 4 Tues- 5 Wed -6
18 cookies eaten
24 -18 = 6 cookies left over, but on Thursday
he needs to eat 7 cookies to continue his
pattern.
Solving Two- Step Equations
Rules to Remember
• When solving an equation, the goal is to
get the variable by itself.
• Addition and Subtraction are inverse
operations. (opposites)
• Multiplication and Division are inverse
operations. (opposites)
Don’t Forget
• The equation is like a balance scale.
Whatever you do to one side of the
equation must be done to the other side of
the equation.
How to solve two-step equations
• “Undo” the operations in the reverse order
of the order of operations.
• You are using the work back-words
strategy
• In order of operations we do multiplication
or division first, then addition and
subtraction. When solving an equation we
do the opposite!
Integer Rules to Remember
•
1.
2.
•
1.
2.
•
1.
2.
Adding Integers
Same sign= add and keep the sign
Different sign = subtract and keep the sign of the larger
number
Subtracting Integers
Keep, Change, Change
Follow the rules for addition
Multiplying and Dividing Integers
Same Sign = Positive Answer
Different Sign = Negative Answer
Let’s Try One…
The problem contains
addition and
multiplication. Which
one do we undo 1st?
• 3x + 2 = 23
- 2 -2
21
3x = 21
3
3
x=7
Another Example
The problem contains
subtraction and
multiplication. Which
one do we undo 1st?
• -2y – 7 = 3
+7 +7
10
-2y = 10
-2
-2
y = -5
Last Example
The problem contains
addition and
multiplication. Which
one do we undo 1st?
• -3c + 9 = 3
-9 -9
-6
-3c = -6
-3
-3
c= 2
Now it’s your turn
1.
2.
3.
4.
5.
6.
5x + 4 = 19
2t + 7 = -1
6m + 1 = -23
-4w – 4 = 8
-7y + 3 = -25
3t – 13 = 2
1.
2.
3.
4.
5.
6.
x=3
t = -4
m = -4
w = -3
y=4
t=5
Independent Practice
• Galt 2.9