Transcript Solving add and sub equations powerpoint

Solving Addition
and Subtraction
Equations
Lesson 6-2
Page 225
Which word do you
think “Equation” has a
connection to?
YOU’RE
CORRECT!
An equation is a
mathematical
sentence that
contains an
equal sign.
The part on the left side of
the equal sign has the same
value as the part on the
right side. One or both
sides may contain a
variable.
What is a variable?
A. A number that changes constantly.
B. A letter or symbol that stands for a
number.
C. A number that varies as you move
away from zero.
YOU’RE
CORRECT!
A variable is a
letter or symbol
that stands for a
number.
To solve an equation,
you must find what the
variable represents so
that the two parts are
equal.
Equations are like
balance scales. In
order to keep a
scale balanced you
must have the same
amount of weight
on both sides.
If I took one block away from the left
side, what would I have to do to keep
the scale from tipping?
If I added 6 more apples to the right
side, how could I keep the scale from
tipping?
To keep an equation equal, we
must do exactly the same thing
to each side of the equation. If
we add a number to one side,
we must add that same number
to the other side and vice
versa.
Addition and subtraction
are called “opposite
operations” because they
can ‘undo’ each other.
What are the other
two opposite
operations?
Multiplication
and division are
opposite
operations, too!
for Solving Addition and
Subtraction Equations
1. Look to see
what side the
variable is
on.
2. Decide
what
operation is
being shown.
3. Do the
opposite of
that
operation to
both sides.
4. Write what
number the
variable
stands for
(ex: a = 2).
5. Check the solution
by “plugging” the
number back into the
equation to see if the
sides are equal.
Example 1
m + 18 = 34
-18 -18
m = 16
Look for variable
Do the opposite
Write what m is
m + 18 = 34
16 + 18 = 34 Plug in m
34 = 34
Solution is correct!
If you check your solution
and you do not come out
with the same numbers,
then your solution is not
correct. Therefore, you
must rework the problem.
Always check your
answers to equations. It is
the only way to make sure
you get a problem correct.
Why miss a problem when
you can get all of them
correct?
Example 2
68 = y + 43
-43
-43
Look for variable
Do the opposite
25 = y
Write what y is
68 = y + 43
68 = 25 + 43 Plug in y
68 = 68
Solution is correct!
Example 3
t - 14 = 22
+ 14 +14
t = 36
Do the opposite
t - 14 = 22
36 - 14 = 22
22 = 22
Plug in t
Look for variable
Write what t is
Solution is correct!
Try These...
1.
2.
3.
4.
r + 5 = 18
m - 26 = 59
102 = x - 15
a + 39 = 56
r = 13
m = 85
117 = x
a = 17
Let’s do
Checking for
Understanding
Page 226 8-13
Prediction:
You will show all
of the steps
(including
checking) as you
have been shown
today or credit will
not be given for
your homework.
Are there any
questions about
solving addition
or subtraction
equations?
Homework:
Page 227 14-37 all
Don’t forget to check
your solution!