How to factorHow to factor

ax2+bx+c

c° jorge.garcia@csuci.edu

(No Clicking Please)

-8 +15

-120

-20

-4 +5

f

F Wearedone! Now we just ¢¢¢

(6) ¢(¡ 20) = ¡ 120F Two numbers whoseproduct is -120

and whosesum is +7

F Two numbers whoseproduct is -20

First one¯ts evenly into -8

Second one¯ts evenly into +15

(wait)

ExampleA 6x2+7x ¡ 20

Ready?

-8 +15

-120

-20

-4 +5

2 3

¢

F Solution is

(6) ¢(¡ 20) = ¡ 120

and +15 by +5

(2x+5) (3x ¡ 4)

F Divide ¡ 8 by ¡ 4

ExampleA 6x2+7x ¡ 20

(wait)

(10) ¢(¡ 3) = ¡ 30

-15

+2 -30

-3

-3 +1

F Two numbers whoseproduct is -30

F Two numbers whoseproduct is -3

First one¯ts evenly into -15f

and whosesum is ¡ 13

Second one¯ts evenly into +2

F Wearedone! Now we just ¢¢¢

(wait)

ExampleB 10x2 ¡ 13x ¡ 3

Ready?

(10) ¢(¡ 3) = ¡ 30

-15

+2 -30

-3

-3 +1

5 2

and +2by +1

¢(2x ¡ 3)

F Solution is

(5x+1)

(wait)

F Divide ¡ 15 by ¡ 3

ExampleB 10x2 ¡ 13x ¡ 3