Download 0350 2 step equations pt2

Solving Two- Step Equations
Lesson 4-4
Rules to Remember
• When solving an equation, the goal is to
get the variable by itself.
3x + 2 = 9
• Addition and Subtraction are opposites
• Multiplication and Division are 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.
+5
+5
How to solve two-step equations
• “Undo” the operations in the reverse order
of the order of operations.
• Work back-words SADMEP
– Add/Subtract FIRST
– Multiply/Divide SECOND
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
Solving Two-Step Equations
Solve each equation.
18 + 3x
18 + 3x
– 18
3x
= 30
= 30
–18
= 12
Subtract 18 from both sides to
undo the addition.
3x = 12
3
3
Divide both sides by 3 to undo
the multiplication.
x=4
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
Solving Two-Step Equations
Solve. Check the answer.
x
–2= 1
3
x
–2= 1
3
+ 2 +2
x
= 3
3
3· x= 3·3
3
x=9
Add 2 to both sides to undo
the subtraction.
Multiply both sides by 3.
Check It Out: Example 1A
Solve each equation.
12 + 3x = 27
12 + 3x = 27
– 12
–12
3x = 15
Subtract 12 from both sides to
undo the addition.
3x = 15
3
3
Divide both sides by 3 to undo
the multiplication.
x=5
Check It Out: Example 1B
Solve. Check the answer.
x
–1= 2
2
x
–1= 2
2
+ 1 +1
x
= 3
2
2· x= 2·3
2
x=6
Add 1 to both sides to undo
the subtraction.
Multiply both sides by 2.