So since the first x is raised to the 4th power and the second is raised to the 2nd power and the last number is a negative, you automatically start your factor with (x^2+__)(x^2-__) Then you have to look at factors that would multiply to make -7 and add to make 6, which would be +7 and -1 so you end up with (x^2+7)(x^2-1)