Factors
and
Greatest
and Greatest Common Factors
8-1
8-1 Factors
Common Factors
Warm Up
Lesson Presentation
Lesson Quiz
Section 8-1
Holt
Algebra
Holt
Algebra
11
1
8-1 Factors and Greatest Common Factors
Bell Quiz 8-1/81/8-2
3 pts
1. List the factors of 28.
Tell whether the number is prime or
composite.
2 pts
2. 11
5 pts
possible
Section 8-1
Holt Algebra 1
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8-1 Factors and Greatest Common Factors
Questions on 00-7/07/0-8/08/0-9
Section 8-1
Holt Algebra 1
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8-1 Factors and Greatest Common Factors
Objectives
Write the prime factorization of
numbers.
Find the GCF of monomials.
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8-1 Factors and Greatest Common Factors
Vocabulary
prime factorization
greatest common factor
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8-1 Factors and Greatest Common Factors
The whole numbers that are multiplied to find a
product are called factors of that product. A
number is divisible by its factors.
You can use the factors of a number to write the
number as a product. The number 12 can be
factored several ways.
Factorizations of 12
•
•
•
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8-1 Factors and Greatest Common Factors
The order of factors does not change the product,
but there is only one example below that cannot
be factored further. The circled factorization is
the prime factorization because all the factors
are prime numbers. The prime factors can be
written in any order, and except for changes in
the order, there is only one way to write the
prime factorization of a number.
Factorizations of 12
•
•
•
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8-1 Factors and Greatest Common Factors
Remember!
A prime number has exactly two factors, itself
and 1. The number 1 is not prime because it only
has one factor.
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8-1 Factors and Greatest Common Factors
Example 1A: Writing Prime Factorizations
Write the prime factorization of 98.
Factor tree
2.
The prime factorization Section
of 98
is
2
7
7
or
2
7
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8-1 Factors and Greatest Common Factors
Factors that are shared by two or more whole
numbers are called common factors. The greatest
of these common factors is called the greatest
common factor, or GCF.
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 32: 1, 2, 4, 8, 16, 32
Common factors: 1, 2, 4
The greatest of the common factors is 4.
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8-1 Factors and Greatest Common Factors
Example 2A: Finding the GCF of Numbers
Find the GCF of the pair of numbers.
12 and 16
Method 1 List the factors.
Method 2 Prime factorization.
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8-1 Factors and Greatest Common Factors
You can also find the GCF of monomials that
include variables. To find the GCF of monomials,
write the prime factorization of each coefficient
and write all powers of variables as products.
Then find the product of the common factors.
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8-1 Factors and Greatest Common Factors
Example 3A: Finding the GCF of Monomials
Find the GCF of the pair of monomials.
15x3 and 9x2
Write the prime
factorization of each
coefficient and write
powers as products.
Find the product of the
common factors.
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8-1 Factors and Greatest Common Factors
Example 3B: Finding the GCF of Monomials
Find the GCF of the pair of monomials.
8x2 and 7y3
Write the prime factorization
of each coefficient and write
powers as products.
There are no common
factors other than 1.
The GCF 8x2 and 7y is 1.
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8-1 Factors and Greatest Common Factors
Helpful Hint
If two terms contain the same variable raised to
different powers, the GCF will contain that
variable raised to the lower power.
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8-1 Factors and Greatest Common Factors
Check It Out! Example 3
Find the GCF of each pair of monomials.
a: 18g2 and 27g3
b: 16a6 and 9b
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8-1 Factors and Greatest Common Factors
Section
88-1 (page 527)
2, 10, 13, 1717-20, 2525-30
No homework for 5th
Section 8-1
Holt Algebra 1
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