Today, lesson want about Common factors and
grouping.
The object of these are:
·
Find the greatest common factor (GCF) of
the numbers
·
Find the greatest common factor (GCF) of
the terms
·
Factor out the greatest common factor
·
And then finally, factor a four term
expression by grouping
So, lets get study with some definition in
particular product and factor.
Let say we have many expressions
Fifteen equals three times five.
We say that fifteen is the product
and the factors are three and five.
What we mean by factoring is that
factoring completely means to have all factors as prime number.
The key is we have fifteen broken
down as factors three and five.
Another expression is twenty that
brokrn in to the prime numbers of two times two times five. This number can not
be broken down any further.
To find the greatest common factor
of number, we are provided with the list of the integers. In the list, the largest common factor of integers is noun as the greatest common factor.
So, lets taken example:
Fourty five can be broken down in to three times three
times five or three square times five.
Another number is sixty. Sixty can be broken down as two square times
three times five.
You know that three square times
five equals fourty five. Three square is nine, nine times five is fourty five.
Two square is four.Four times three
is tweleve. Tweleve times five is sixty.
·
To find the greatest common factor,
choose prime nombers. Fourty five have two factors and sixty is three factors
here. Choose prime factors with the smallest exponents and find their product.
So the common here is three, the
smallest exponent is one. The common here also is five and the smallest
exponent is also one.
Therefore three and five are common
factors of fourty five and sixty. Now we can say that three times five equals
fifteen. Therefore, fifteen is the
greatest common factor between fourty five and sixty.
Once again, to finding the greatest
common factor of numbers, we find the smallest exponent and choose the sadow of prime factors and
then find their product.
So, lets consider thirty six,
sixty, and one hundred and eight.
Thirty six can
be broken down as wo square times three square. We know that two square is four
and three square is nine. So four times nine is thirty six.
Like that ways,
we have sixty. Sixty can be broken down as two square times three times five.
Two square is four, Four times three is tweleve and tweleve times five is
sixty, and finally we had the number of one hundred eight wich we can broke
down as two square times three cube is twenty seven. Four times twenty seven is
one hundred eight.
We can see here
two is common among of this numbers and the exponent is two. So, two square is
one of the prime factors.
Three is the
common of this numbers and the smallest exponent is one. Therefore, we have two
square times three. Now that two square is the smallest with the base two and
three is has exponents of one. Its common and smallest exponent are associated.
So, tweleve is the greatest common factor among thirty six, sixty, and one
hundred and eight.
Another way is
to doing this is:
We can take
thirty six,sixty and one hundred and eighty and We devide two among that. So,
therefore we know that thirty six divide by two is eighteen, sixty divide by
two is thirty, and one hundred and eight divide by two is fivety four. Again we
can divide by two. So, this is eighteen divide by two is nine, thirty divide by
two is fifteen, and fivety four divide by two is twenty seven. See that it is
three common among them. So, we have
here nine divide by three is three, fifteen divide by three equals five, and
twenty seven divide by three is nine. We can see that it is can not be broken
down to any factors. So, what we have here is collect this term here two two
three. We get same result using this approach.
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