I need to prove that these determinants are equals.

Note: these are determinants, not matrices, I just don't know how to set them up as determinants using the math code...

= (1- )

This tells me that I need to somehow get (1- ) multiplied into the determinant. I know that to get that out, one would have to multiply a row by (1- ), or possibly (1-t) on two different rows... Am I thinking it the right direction?