Download Variable Substitution

1. Write a math problem in which two
numbers add together to equal ten.
2. Do the same problem as above except
make one of the numbers negative.
3. Do #1 except have one of the numbers
be a square root
.
4. Do #1 except have one of the numbers
be a square root
, and the other be a
negative number.
You plan to go hiking in the Grand Canyon. You
estimate you’ll hike at a rate of 2 miles per hour
on a steep trail. How long will it take you to hike
a 36 mile stretch of marble canyon?
Time =
𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆
𝒓𝒂𝒕𝒆
Time = 𝒕 (hours)
Distance = 𝟑𝟔 (miles)
Rate = 𝟐 (mph)
𝟑𝟔
𝒕=
𝟐
𝟏𝟖 𝐇𝐨𝐮𝐫𝐬
Negative Numbers
−𝟓 + 𝟑 =
-5 -4 -3 -2 -1
−𝟐
0
1
2
3
4
5
Negative Numbers
−𝟏 + −𝟑 = −𝟒
-5 -4 -3 -2 -1
0
1
2
3
4
5
Negative Numbers
−𝟏𝟒 + 𝟐𝟖 = 1𝟒
−𝟐𝟑 + −𝟕 = −𝟑𝟎
1𝟓 − −𝟕 =
𝟐𝟐
What is a Variable?
X
Y
A variable is a letter or a
symbol that stands for a
number.
Variable Substitution
Solve when 𝑥 = −2
3x = 𝟑 −𝟐 = −𝟔
1st – Substitute a number for
each variable. Use
parentheses!!!!!!!!!!!!!
Examples
1. Solve for T = 3.
3T + 5
3(3) + 5
9+5
14
2. Solve for 𝒋 = −𝟐.
−𝟒𝐣 − 𝟑
−𝟒 −𝟐 − 𝟑
𝟖−𝟑
5
Examples
Solve for g = 2 and s = 4
1g + 1s
4
5
1(2) + 1(4)
4
5
1+4
2 5
5+8
10 10
3
1
10
Examples
1. Evaluate for n = 7.
n + 5 + (n + 3)
7 + 5+ (7 + 3)
7 + 5+(10)
12+ 10
22
2. Evaluate for 𝒃 = −𝟑.
𝒃 − 𝟖 + (𝒃 + 𝒃)
−𝟑 − 𝟖 + (−𝟑 − 𝟑)
−𝟏𝟏 − 𝟔
−𝟏𝟕
Closing
• What does the word variable
mean?
• What does the word substitute
mean?
• How do we substitute for a
variable?