Transcript algebraic expression - Bibb County Schools

Today’s Lesson
Writing
Algebraic
Expressions
Warm-Up Activity
Let’s warm up today by
finding patterns in numbers.
Find the missing numbers in the
following patterns.
3, 6, 9, __ , 15, 18, __ , 24
1, 2, 4, __ , 11, 16, __ , 29
1, 1, 2, 3, 5, __ , 13, __
Check your answers.
3, 6, 9, 12, 15, 18, 21, 24
1, 2, 4, 7, 11, 16, 22, 29
1, 1, 2, 3, 5, 8, 13, 21
What is the pattern?
3, 6, 9, 12, 15, 18, 21, 24
+3
+3 +3 …
+3 each time
What is the pattern?
1, 2, 4, 7, 11, 16, 22, 29
+1
+2
+3
+4 …
+1 more each time
What is the pattern?
1, 1, 2, 3, 5, 8, 13, 21
+0 +1 +1 +2 +3 +5
+8
Add the 2 previous
numbers together
Whole-Class Skills Lesson
Today we will write algebraic
expressions and find patterns
in real-life situations to show
algebraically.
To review, what does the word
variable mean?
A variable is an unknown quantity
that has the potential to change.
What does the term
algebraic expression mean?
An algebraic expression is any
number sentence using variable(s)
and number(s) in any combination.
How would you write the
following expressions?
A number that is 5 more than 8
A number that is 5 more than t
A number that is 3 less than f
A number that is t less than f
How would you write the
following expressions?
A number that is 5 more than 8
8+5
A number that is 5 more than t
t+5
A number that is 3 less than f
f–3
A number that is t less than f
f–t
Judy and her sister are born in the
same month, but in different years.
Judy is 5 years old and her sister is 2.
When Judy turns 8, her sister will be 5.
How old will Judy’s sister be when
Judy is 14?
How did you solve that problem?
Just one of the ways to solve this
problem is to make a T-chart.
This is a T-chart.
Judy’s age
Sister’s age
Copy the T-chart below
Copy the data for Judy and her
sister’s ages. This data comes
from the problem.
Judy’s age
Sister’s age
5
2
8
5
14
Do you see a pattern with Judy
and her sister’s ages?
Judy’s age
Sister’s age
5
2
8
5
14
Judy’s sister’s age is always 3
years less than Judy’s age.
So based on the pattern, when
Judy is 14, her sister will be three
years less than that—11 years old.
How old will Judy’s sister be
when Judy is 20?
20 – 3 = 17
Judy’s sister will be 17.
How old will Judy’s sister be
when Judy is 25?
25 – 3 = 22
Judy’s sister will be 22.
Assign a variable to Judy’s age.
Judy’s age
Sister’s age
5
2
8
5
14
11
j
Judy’s age can be represented by a variable, j
What is the best way to figure out
Judy’s sister’s age using j as a
starting point?
We can write an algebraic for
Judy’s sister’s age.
j–3
Using j – 3, solve for Judy’s
sister’s age when
j = 31
31 – 3 = 28
j = 45
45 – 3 = 42