39x^3 = 13*3*x*x*x
-6x^2 = 2*3*x*x*-1
-3x = 3*x*-1
so in all these factorizations, 3*x is common. so 3x is the common factor.
by seperating the common factor,
3x(13x^2 - 2x-1)
will be the factorization.
xy + 5x - 5y - 25
=x (y+5) -5 (y+5)
=(x-5) (y+5)
hope I helped ya!!!
