Factoring integers
Factoring integers is the easiest thing we can factor. It means to make the integer look like a multiplication
problem by looking for its prime factorization
In other words, factor the integer until all factor are prime numbers
It is very important to know how to do this before learning how to
find the greatest common factor and
how to
factor trinomials
Here is the algorithm:
When factoring, start by dividing the number by 2. Then, keep dividing any factor divisible by 2 that is
not prime by 2 until no factors is
divisible by 2.
When no factors are divisible by 2, start by dividing by 3 until no factors are
divisible by 3.
When no factors are divisible by 3, start by dividing by 4 until.....
and so forth...
Let us start practicing!
Factor 4
Dividing 4 by 2 gives 2, so
4 = 2 * 2
Factor 12
Dividing 12 by 2 gives 6, so
12 = 2 * 6
However, 6 is a factor divisible by 2, so factor 6
factoring 6 gives 2 * 3
Putting it all together,
12 = 2 * 6 = 2 * 2 * 3
when factoring integers a problem can get complicated when the number is big. when this happens make a tree as the following example demonstrates. We call this a factor tree
Factor 72
Pulling out all factors inside the red shape that looks like a golf bat, we get:
72 = 2 * 2 * 2 * 3 * 3
Once again, pulling out all factors inside the red shape that looks like a golf bat, we get:
240 = 2 * 2 * 2 * 2 * 3 * 5
You should notice tough that 72 and 240 can be factored faster than that if you know your
multiplication table.
72 = 8 * 9
8 = 2 * 2 * 2 and 9 = 3 * 3
So, 72 = 2 * 2 * 2 * 3 * 3
240 = 24 * 10
10 = 2 * 5 and 24 = 4 * 6 = 2 * 2 * 2 * 3
So, 240 = 2 * 2 * 2 * 2 * 3 * 5

Oct 15, 18 11:05 AM
why the rule of 72 works math explanation of where the 72 came from.
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