Question 165479
For any numbers a and b , a#b= a + b –ab . If a#b = 0, which of the following 
CANNOT be a value of b ? 
(A) 2 (B) 1 (C) 0 (D) --1 (E) -3 /2 
<pre><font size = 4 color = "indigo"><b>
Suppose

{{{matrix(1,5,  "a#b", "=", a+b-ab, "=", 0)}}}

{{{a - ab = -b}}}

{{{a(1-b) = -b}}}

{{{a = (-b)/(1-b)}}}

The denominator, {{{1-b}}} cannot be zero, and it would be if {{{b=1}}}.

So {{{b}}} cannot equal {{{1}}}.  Choice (B)

Edwin</pre>