Levered/Unlevered Beta

Hi, I’m really confused with the question from CFAI online topic test, Western vignette, Q1. In answer, we see next formula , all my life I think we should also add *(1-t) in denominator. Formula from Investopedia Unlevered Beta http://www.investopedia.com/terms/u/unleveredbeta.asp So, what formula is right?

Understood, just skip this post

Care to explain?

I think the formula without tax is only correct with the assumption: “tax can be ignored”. This assumption is implicitly postulated.

But it’s better that “Financial from…” confirms that.