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10.5: Factoring Trinomials
(Reverse FOIL)
Integrated Math 2
Remember FOIL?
(x + 2)(x – 7) = x2 – 5x – 14
F O+I L
To Factor Trinomials, we start with the trinomial
and try to find the original two binomials.
How to Factor: Factor x2 + 4x – 12
1. Parenthesis with an x in each group:
(x
)(x
)
2. Draw a big X. The third term goes on top the
middle # goes on bottom.
3. Think of two #’s that multiply to get the top, but the
same #’s add to get the bottom.
4. Hint!!! List the factors of the top #.
5. Place the two correct numbers and their signs in
the parenthesis. It doesn’t matter which number
goes where!!!
Reverse FOIL
Some people may find this chart helpful, but reverse
FOIL is technically trial and error!
Problem
Factored answer
ax2 + bx + c
(x + )(x + )
ax2 - bx + c
(x - )(x - )
ax2 + bx – c
(x + )(x - )
ax2 - bx – c
(x + )(x - )
Try These:
1.
x2 + 5x + 6
( x + 3 )( x + 2 )