Question 1209234
<pre>
I hope you understand FOIL, i.e., FIRSTS, OUTERS, INNERS, LASTS. I'm assuming you do.

2ab - a + b + ___

Write this:

(__ ± __)(__ ± __)

Let's fix up the FIRSTS to be 2ab.  We will split 2ab up into factors 2a and b
and put them for the FIRSTS

(2a ± __)(b ± __)

Now let's fix up the OUTERS.  We notice to get the term " -a " for the OUTERS,
we will need the term on the far right to be -1/2.

(2a ± __)(b - 1/2)

Now let's fix up the INNERS.  We notice to get the term +b for the
INNERS, we will need the term +1 in the remaining blank:

(2a + 1)(b - 1/2)  <--factorization as the product of two linear expressions

The LASTS are now already fixed up. 

So we proceed to FOIL that out:

(2a)(b)+(2a)(-1/2)+(+1)(b)+(1)(-1/2)

2ab - a + b + (-1/2)

So we see that the answer is -1/2

Edwin</pre>