If you have difficulty factoring trinomials with lead
coefficient
1, then you can try the following approach. Some people call
this the “bottoms up” method. Note: ALWAYS remember to factor out the GCF first
(it will make all of the numbers smaller and easier to work with)
Given
Example: ![]()
1. Find ac ac =
= ![]()
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2. Find two factors
of ac that since ac =
and b=19, we need to find two numbers whose product
is
and that
add up to b. add up to
19.
AND
. So the numbers we
want are
21 and – 2
![]()
3. Divide each number by a
note: in this problem a
was 6
and reduce the fraction.
![]()
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4. Write two factors, bringing the ![]()
![]()
“bottoms up” to be the coefficients
of the variable.
Answer: ![]()
Remember, if you want to check to see if the trinomial is “factorable”, just check to
see if the discriminant (
) has a “nice” square root.
In our previous example…………
=
and
so we KNOW that
could be factored, it was just a case of figuring out HOW.
You try
……………scroll down the page to see the steps.
ac
=
= ![]()
b=13 and
![]()
Dividing each of
by 12 and reducing….
![]()
![]()
Now bring the “bottoms up” to write the factors….
Answer: ![]()
![]()
Check:
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