1. How Do I Multiply Two Binomials?

2. Table of Contents
82: Warm Up; Guided Practice
83: How Do I Multiply Two Binomials?

3. Warm-Up Period 3 Factor the following:
1. x2 – 3x x2 + x – x2 + 10x x2 + 25x + 20
(x + 7)(x – 6)
Prime
For the first section of the warm-up, the students need to find the value of “a” (which shows how much the graph changes in it’s width and direction) and to find the vertex. To find the y-intercept, you need to mulitply the value of a (unknown) * r (1) * s (3), which will equal 18. The students will solve for a and get it to be 6.
To determine the vertex, the students will add r + s and divide that be two, getting 2. They then plug that into the equation and solve for g(x), getting -6.
-5(x2 – 2x – 5)
5(x + 1)(x + 4)

4. Warm Up Period 2 Factor the following:
1. x2 + 8x – x2 – 9x – x2 – 36x x2 + 16x – 8
(x + 3)(x – 12)
Prime
-6(x2 + 1)(x – 4)
4(x2 + 4x – 2)

5. Warm-Up Multiply the following without a calculator:
• • 17
1288
901

6. How Do I Multiply Binomials?
1/17/2019

7. Binomial Two terms that are not alike which are added or subtracted
FOIL Method
A way of multiplying two binomials
F O I L
First Terms
Outside Terms
Inside Terms
Last Terms

8. Example 1: Multiply using FOIL
(x + 3)(x + 2)
(x + 3)(x + 2)
F O I L
x • x
= x2
x • 2
= 2x 5x
3 • x
= 3x
3 • 2
= 6
x2 + 5x + 6

9. Guided Practice 1
Multiply using FOIL: (x + 4)(x – 2)
x2 + 2x – 8

10. Guided Practice 2
Multiply using FOIL: (x – 7)(x – 6)
x2 – 13x + 42

11. Questions What do the letters in FOIL stand for?
What do you think would happen if a was not 1? How would that change the way you multiply?
How could you use this to check your work?

12. Example 2: Multiply vertically
(x + 3)(x + 2)
x + 3 x + 2
_________ 2x
+ 6
_____________ x2
+ 3x
x2 + 5x + 6

13. Guided Practice 3
Multiply vertically: (x + 4)(x – 2)
x2 + 2x – 8

14. Guided Practice 4
Multiply vertically: (x – 7)(x – 6)
x2 – 13x + 42

15. Questions What do you need to line up in order to multiply vertically?
What do you think would happen if a was not 1? How would that change the way you multiply?
How could you use this to check your work?

16. Example 3: Multiply with the box method
(x + 3)(x + 2) x x x2 3x 2x 6
x2 + 3x + 2x + 6
x2 + 5x + 6

17. Guided Practice 5 Multiply with the box method: (x + 4)(x – 2)

18. Guided Practice 6 Multiply with the box method: (x – 7)(x – 6)

19. Questions How do you need to set up this problem in order to multiply?
What do you think would happen if a was not 1? How would that change the way you multiply?
How could you use this to check your work?
Which method do you like best and why?