It starts at 5:29. Basically, what he is saying is that:
He's says that you can take the LCM of the fractional exponents (6), and multiply both sides of the equation by x^6 to remove the fractions. But, if you do that, wouldn't this happen:
Which doesn't help at all.. And even if you tried something like this:
Even using the binomial theorem and expanding, it would probably reintroduce more strange fractional exponents. Am I right?