Factoring

(Reverse FOIL)

Factoring trinomials is one of the most

important concepts in mathematics (and one of my favorite things to do)!

Think of factoring as taking a puzzle apart. There are some very simple rules:

There is only one way to get x2 x * x The sign on the third term helps determine the

signs of each factor. The sign of the second term tells you the sign of

the largest factor.

Factoring

x2 + 8x + 15 (x )(x )

(x + )(x + )

3 * 5 = 15 and 3 + 5 = 8 (x + 3)(x + 5)

*Check you answer using FOIL!

Factoring1. How do you get x2?

2. The sign on 15 is positive so both factors must be the same.

3. What can I multiply to get 15 and add to get 8?

If the 3rd term is positive, the signs are the same.If the 3rd term is negative, the signs are different.

Try again. x2 + 9x – 10

(x + 10)(x – 1)

Try this one: x2 + 7x + 12

(x + 3)(x + 4)

Factoring

Remember, if the 3rd term is negative the signs are different!!

The largest factor has to be positive because the 2nd term is positive.

See if you can do these. Check your answers

with the person sitting next to you.1. x2 – 4x + 4 2. x2 – 11x – 26

3. x2 + 21x + 108 4. x2 + 5x – 14

5. x2 – 11x + 24 6. x2 + 2x - 15

Factoring

How did you do?? 1. (x – 2)(x – 2) 2. (x – 13)(x + 2) 3. (x + 9)(x + 12)4. (x – 2)(x + 7) 5. (x – 8)(x – 3) 6. (x – 3)(x + 5)

Factoring

Just remember the simple rules. Don’t get stressed out. This is fun!! Practice makes perfect in factoring! Come see me for tutorials if you need help!!

Factoring