Mathematics

# factorise  2x^2 - x - 1  help me

#### Quan336

5 years ago

ok what i like to do is this...

look at the expression you know that there are 2 x's so you pull these out first keeping in mind that there is a coefficient
(2x   )(x     )

now think what 2 numbers gives me "-1" you think "1" and "-1"  (remember that you might have a few different factors)

if you plug those in... (remember that where you place these numbers does matter)
(2x+1)(x-1)

now check using FOIL !!

#### yassautumn

5 years ago

$2x^2 - x - 1 =\\ 2x^2-2x+x-1=\\ 2x(x-1)+1(x-1)=\\ (2x+1)(x-1)$