factor

[Chocolate]

show work:

Q: 12a^2-4a-5

A: P=-60 S=-4 (-10, 6) what would be the nex step?

and, this one i dunno evn how to start:

Q: x^3-4x^2-x+4

 

[arthur ohlsten]

the first one I dont understand

x^3-4x^2-x+4 if it is factorable factors must be the factors of 4
possible factors +/- 1 +/-2 +/-4 let us try x=1
1^3-4[1^2] -1+4
1-4-1+4 =0 then x=1 is a root divide by x-1
x^2 -3x-4
-------------------
x-1 l x^3-4x^2-x+4
x^3-x^2
-------------------
-3x^2 -x+4
-3x^2+3x
-------------------
- 4x+4
- 4x+4
---------
0

x^3-4x^2-x+4
[x -1][x^2-3x-4]
[x-1][x-4][x+1] answer
Arthur

 

[Chocolate]

1-4-1+4 =0 then x=1 is a root divide by x-1
x^2 -3x-4
-------------------
x-1 l x^3-4x^2-x+4
x^3-x^2
-------------------
-3x^2 -x+4
-3x^2+3x
-------------------
- 4x+4
- 4x+4
---------
0

x^3-4x^2-x+4
[x -1][x^2-3x-4]
[x-1][x-4][x+1] answer
Arthur

I don't get why x=1 is a root divided by x-1

 

[Gene]

If
x-1
is a root then
x-1=0
so
x=1

 

[Chocolate]

Yes that helps, thanks! but how can you divide x^3-4x^2-x+4 by x-1 using synthetic division? i remember learning it, but i can't remember it now.

 

[stapel]

how can you divide x^3-4x^2-x+4 by x-1 using synthetic division?

It would be difficult to attempt constructing a lesson here. Try Google for lessons on the topic.

Eliz.

 

[Gene]

They do a better job than I can at
http://www.purplemath.com/modules/synthdiv.htm

 

[Chocolate]

Thanks, that's all the questions i have for now.