Hi

What do i get when i expand:

x^2 - 1

Is it

(x-1)(x+1)

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- Oct 23rd 2007, 10:42 AMtaurusExpand
Hi

What do i get when i expand:

x^2 - 1

Is it

(x-1)(x+1) - Oct 23rd 2007, 10:43 AMJhevon
- Oct 23rd 2007, 10:50 AMtaurus
yes thanks

- Oct 23rd 2007, 10:57 AMtaurus
Just a quick question:

is it ok to write

21 - 4x - x^2

as

x^2 + 4x - 21? - Oct 23rd 2007, 11:06 AMJhevon
not unless it is equated to something where you can distribute the minus on the other side as well:

so, say you had: 21 - 4x - x^2 = 0

then it is okay to multiply both sides by -1 to get: x^2 + 4x - 21 = 0

but if you just have the expression by itself, you cannot do that, the best you can do is to say:

$\displaystyle 21 - 4x - x^2 = - \left( x^2 + 4x - 21 \right)$

leave the minus outside of the brackets - Oct 23rd 2007, 11:10 AMtaurus
so for example this:

1/(21-4x-x&2)

Which one do i use? - Oct 23rd 2007, 11:14 AMJhevon