Question 1209234
<br>
{{{2ab-a+b+x}}}<br>
Group the first two terms and take out the common factor.  (You could equally well group the first and third terms and proceed in a similar manner.)<br>
{{{a(2b-1)+(b+x)}}}<br>
We need to write the expression {{{(b+x)}}} in the form where it is a constant times the factor {{{(2b-1)}}}.<br>
{{{b+x=n(2b-1)}}}<br>
Clearly the constant n must be 1/2.  That gives us<br>
{{{a(2b-1)+(1/2)(2b-1)=2ab-a+b-1/2}}}<br>
ANSWER: -1/2<br>