# basic help

• November 1st 2012, 03:22 PM
pnfuller
basic help
how to set 2x2-4x-1 eqaul to 0? do you have to factor it first or does it matter?
• November 1st 2012, 03:28 PM
skeeter
Re: basic help
Quote:

Originally Posted by pnfuller
how to set 2x2-4x-1 eqaul to 0? do you have to factor it first or does it matter?

$b^2-4ac$ is not a perfect square, so the expression will not factor over the rationals ... you'll have to complete the square or use the quadratic formula.
• November 1st 2012, 03:40 PM
pnfuller
Re: basic help
do i need the whole quadratic formula or the just b^2-4ac part you mentioned?
Quote:

Originally Posted by skeeter
$b^2-4ac$ is not a perfect square, so the expression will not factor over the rationals ... you'll have to complete the square or use the quadratic formula.

• November 1st 2012, 03:51 PM
skeeter
Re: basic help
$b^2-4ac$ is part of the quadratic formula ... and yes, you need the whole formula to solve for x.
• November 1st 2012, 04:30 PM
pnfuller
Re: basic help
would the answers be 2.225 and -.225
• November 1st 2012, 05:47 PM
wasp
Re: basic help
Quote:

Originally Posted by pnfuller
would the answers be 2.225 and -.225

In fact they are. But all things considered I would suspect your instructor would prefer
$x = \frac{2 \pm \sqrt{6}}{2}$

-Dan