<p>“However the question did not state that a cannot equal b which is why I answered 11”</p>
<p>Umm, I don’t see the logic here. The equation is supposed to hold <em>for all</em> a and b. The correct answer is 6. For example, if n is odd, and a and b are different, then (a-b)^n and (b-a)^n are not equal, so the equation does not hold for all a and b if n is odd.</p>