CHAPTER 11-1 VARIABLES AND EXPRESSIONS

WARM -UP

Add or subtract Multiply or divide1. -12+(-5) 5. -13*52. 9-(-4) 6. 3. 5+(-7) 7. 4.2*0.34. -8+(10) 8.

Warm –up answers

Add or subtract Multiply or divide1. -12+(-5) -17 5. -13*5 -652. 9-(-4) 13 6. -503. 5+(-7) -2 7. 4.2*0.3 1.264. -8+(10) 2 8. 660

Variables and expressions

• Objectives: • Translate between words and algebraic

expressions• Evaluate algebraic expressions

Variables and expressionsvocabulary

• variable: is a letter or symbol used to represent a value that can change.

• Constant: is a value that does not change.• Numerical expression: may contain only

constants and/or operations.• Algebraic expression: may contain variables,

constants and/or operations.

Variables and expressionsvocabulary examples

• Give examples for the following:• Variables :

• Constants:

• Algebraic Expressions:

Variables and expressionsDiagram

+ Plus, sum , increased by , more than

__ Minus, difference, less than

* Times, product ,equal group of, multiply by

Divided by, quotient

Use diagram to help translate algebraic expressions to words

Variables and Expressions Translate from algebraic expression to words

I. Give different ways to write each algebraic expression into words Example 1: A) x+5 • The sum of x and 5• Five more than x• X plus 5• X increased by 5

Translate from algebraic expressions to words

B) m-6• The difference of m and 6• 6 less than m• m minus 6

C) 3*k• The product of 3 and k• 3 times k

Translate from algebraic expressions to words

• D) g• g divided y 8• The quotient of g and 8

Translate from algebraic expressions to words

• Student practice :• Check it out 1a to 1d1a. 4-n 1c. 9+q

1b. 1d. 3(h)

Variables and expressions Diagram

• Use to help you translate words into algebraic expressions

Add Put together, combine

Subtract Find how much more or less

Multiply Put together equal groups

divide Separate into equal group

Translate words into algebraic expressions

• Example 2:A) Evelyn has 2 more years than her sister

Adriana. Write and expression for Evelyn’s age.

* a+2B) Sam is 3 years younger than sue, who is y years old. Write an expession for sam’s age.* y-3

Translate words into algebraic expressions

• Words to look for that will help you with translation

addition sum , more

Subtraction Less, difference, minus

Multiplication Per, times, product

Division Quotient, ratio

Translating words into algebraic expressions

C) Mario’s car is going 55 miles per hour. Write an expressions for how fast is Mario’s car going. • 55 hD) William runs a mile in 15 minutes. Write a an

expression for the number of miles that william run in m minutes.

* • Student Practice : check it out 2a-2c

Evaluating Algebraic Expressions

• Evaluate: is to find its value. • Substitute: to replace • To evaluate an algebraic expression substitute

the variables in the expression for numbers and then simplify as needed.

• Hint: Usually they give the numbers you need to substitute the variables for.

Evaluating Algebraic Expressions

• Example 3: Evaluate each expression for x=8 , y=2 and z=4

A) x+z x+z= 8+4 * substitute x with 8 and z with 4 = 8+4= 12 simplify

Evaluating Algebraic Expressions

B) xyzxyz = 8*2*4 substitute x,y and z with 8,2 and 4 = 8*(2*4)=8*8 simplify = 64

= substitute== 4 simplify

Student Practice

• Evaluate the following expressions give x=3,y=-7 and z=5

• A) xy B) 2x+y C) x-z-y* Check it out 3a-5

Evaluating Algebraic Expressions

• Example 4: Challenge• Example 5:Comparing cellphones plans*Lets says company AC has a plan that consists of $35 plan fee for the first 600 minutes plus 10 cents per minute pass the 600 minutes.• Company BC has a plan that consists of $25 plan fee

for the first 600 minutes plus 25 cents per minute pass the 600 minutes.

• which plan is less expensive for 800 minutes?

Variables and Expressions

• Homework for lesson 1-1• Page 9 and 1017-35 evens,41

closure

• Today we learned about what are variables, translating algebraic expressions into words and vice versa.

• We also learned about evaluating algebraic expressions.

• Tomorrow we are going to learn chapter 1-2 solving equations by adding or substracting