Transcript Section 4.1 Powerpoint - Ithaca Public Schools

Variables in Algebra
Goals
• I can evaluate a variable expression.
• I can write variable expressions for word
phrases.
• I can write a variable expression that
models a real life situation.
Variables and Expressions
Special Vocabulary: variable, constant, numerical
expression, algebraic expression
• Variable- a letter or symbol that can be used for a
value that can change.
• Constant – a value that does not change.
 Numerical expression – a mathematical phrase that
contains only constants and/or operations
 Algebraic expression – a mathematical phrase that
may contain variables, constants, and/or operations
Variables and Expressions
• We can replace the variables with numbers and
evaluate the expression.
• To evaluate an expression is to find it’s value. We
evaluate when we simplify to the lowest possible
value after substituting the number for the variable.
YOU TRY:
Evaluate the Expression when y = 3
a. 4y
12
b.
y
c. y + 8
d. 18 - y
We have to be able to “translate”
words into expressions
What words indicate a particular operation?
Add
Subtract
Sum
Plus
More than
Increase(d) by
Perimeter
Deposit
Gain
Greater than
Up (flights of stairs)
Total
Minus
Take away
Difference
Reduce(d) by
Decrease(d) by
Withdrawal
Less than
Fewer (than)
Loss of
We have to be able to “translate” words
into expressions
What words indicate a particular operation?
Multiply
Divide
Times
Product
Of
Twice (×2), double (×2), triple (×3), etc.
Half (×½), Third (×⅓), Quarter (×¼)
Area (by)
Percent (of)
Square (times itself 2 times)
Cube (times itself 3 times)
… to the power of ___
(times itself ___ times)
Split into __ parts
Cost each
Quotient
One-half (÷2), Third
(÷3), Quarter (÷4)
Into
Per
Percent (out of 100)
Variables and Expressions
Let’s try an example of “translating” a phrase
into an algebraic expression:
Nine more than a number y
Can you identify the operation?
“more than” means add
Answer: y + 9
Variables and Expressions
Let’s try another example of “translating” a
phrase into an algebraic expression:
4 less than a number n
Can you identify the operation?
“less than” means Subtract
Answer: n – 4.
Why not 4 – n?????
**Expressions that
contain subtracting
will be the hardest for
us!
Variables and Expressions
Let’s try another example of “translating” a
phrase into an algebraic expression:
A number a divided by 12
Can you identify the operation?
Variables and Expressions
This one is harder……
5 times the quantity 4 plus a number c
Can you identify the operation(s)? What does
the word quantity mean? Hmm……
HOMEWORK
Pg 171 2-30 EVENS