Question 765689
<pre>
For contradiction we assume f(x) is NOT a function.

Then there must be two different outputs for the same input,

Let a be the input and b and c be the two different outputs, b &#8800; c.

Then (a,b) and (a,c) are both elements of the relation where b &#8800; c.

Let y = f(x) = {{{x/6}}}

Solve y = {{{x/6}}} for x

     6y = x

Substitute (a,b) and (a,c)

   6b = a,     6c = a

then 6b = 6c

      b = c.

That contracts the assumption that b &#8800; c

Therefore the assumption that f(x) is not a function
is false, and therefore f(x) is a function.

Edwin</pre>