How does:
x^3 - 9x^2 + 24x -16
Become:
(x - 1) (x^2 - 8x - 16)
And what are the values of x?
What would be good study material for this type of algebra?
Synthetic Division
There is a good example on synthetic division found here.
It doesn't! It is easy to see quickly that the constant term in that product is (-1)(-16)= +16, not -16 as in the first expression. It is true that
$\displaystyle x^3- 9x^2+ 24x+ 16= (x-1)(x^2- 8x- 16)$
The best way to see this is to multiply it back:
$\displaystyle (x-1)(x^2- 8x- 16)= (x)(x^2- 8x- 16)- (x^2- 8x- 16)$
$\displaystyle = x^3- 8x^2- 16x- x^2+ 8x+ 16= x^2- (8+1)x^2- (16-8)x+ 16$
[tex]= x^3- 9x^2- 8x+ 16[/itex]
??? x can be any number! Did you mean "what are the values of x that make this 0" or "what values of x solve $\displaystyle x^3- 9x^2- 8x+ 16= 0$?And what are the values of x?
In this case you can also factor $\displaystyle x^2- 8x- 16= (x- 4)^2$ so
$\displaystyle x^3- 8x- 16= (x- 1)(x^2- 8x- 16)= (x-1)(x-4)^2= 0$ and you can use the fact that "if ab= 0 then either a= 0 or b= 0".
What would be good study material for this type of algebra?[/QUOTE]