Transcript Addition Property of Equality

Bellwork Sept. 23, 2010
Copy the equations and
SHOW YOUR WORK!
Determine if the given numbers are
solutions to the given equations.
1. x = 2 for 4x = 9
no
2. x = 5 for 8x + 2 = 42
yes
3. x = 4 for 3(x – 2) = 10 no
1-11
Addition and
Subtraction
Equations
pg. 52
EQ:
How can you solve equations
by using subtraction or
addition?
Definitions
Addition Property of Equality- same number is
added to both sides of an equation, then the equation
remains equal
inverse operations- one operation undoes the
effect of the other operation
Subtraction Property of Equality- if both sides of
an equation have the same number subtracted from
them, the remaining expressions is still equal
To solve an equation means to find a solution to
the equation which is done by isolating the
variable, (get the variable alone on one side of the
equal sign.)
The variables are isolated.
x=8–5
7–3=y
x+5=8
7=3+y
The variables are not isolated.
An equation is like a balanced scale. If you increase or
decrease the weights by the same amount on both
sides, the scale will remain balanced. If you increase
or decrease only one side then the scale is not
balanced.
Equations with Variables Brain-Pop
http://www.brainpop.com/math/algebra/equationswithvaria
bles/
 Write down 2 facts from the clip…
 1.
 2.
ADDITION PROPERTY OF EQUALITY
Words
You can add the
same amount to
both sides of an
equation, and the
statement will still
be true.
Numbers
Algebra
2+3= 5
+4 +4
x = y
+z =+z
2+7= 9
x + z = y+ z
SUBTRACTION PROPERTY OF EQUALITY
Words
You can subtract the
same amount from
both sides of an
equation, and the
statement will still be
true.
Numbers
Algebra
4 + 7 = 11
–3 – 3
x = y
–z = –z
4+4= 8
x–z=y–z
Use inverse operations when isolating a
variable.
•Addition is inverse for subtraction
•Subtraction is inverse for addition
•Multiplication is inverse for division
•Division is inverse for multiplication
Step for solving equations
1. Isolate the variable
2. Solve for the variable
3. Check your answer by substituting
your answer into the first equation.
Example 1
Solve the equation b – 7 = 24. Check your
answer.
Check b = 31
b – 7 = 24
+ 7 +7
b +0
= 31
b = 31
b – 7 = 24
31 – 7 = 24
24 = 24
Example 2
Solve the equation t + 14 = 29. Check your
answer.
t + 14 = 29
– 14 – 14
t + 0 = 15
t = 15
Check t = 15
t + 14 = 29
15 + 14 = 29
29 = 29 
Example 3- Real World
The Falcons scored 13 points in a game against the Cowboys.
They scored 7 points for a touchdown and the rest of their
points for field goals. How many points did they score on
field goals?
Let f represent the field goal points.
7 points + field goal points = points scored
7 + f = 13
–7
–7
f= 6
They scored 6 points on field goals.
Practice
Textbook
Page 54
8-24 even only
Practice
+36 +36
n + 0 = 53
n = 53
-15
+56 +56
p + 0 = 68
p = 68
-15
-14
-14
+51 +51
m + 0 = 74
m = 74
-47
-47
x + 0 = 28
a + 0 = 24
x = 28
x + 0 = 35
a = 24
x = 35
Number of books + number of extra books = total read
6+b=8
-6
-6
b=2
Work Session
Textbook
p. 54
26-42 even
GRADED
Closing
 What are two rules to remember
when adding and subtracting in
equations?
Homework
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Workbook
Page 11
All problems
STUDY TEST TOMORROW