Question 281254
w^2-4w-21/w^2-6w+9 * w-3/w-7 =

((w-7)*(w+3))/((w-3)*(w-3))*(w-3)/(w-7) =
((w-7)/(w-7))*((w-3)/(w-3))*((w+3)/(w-3)) =
      1      *      1      *(w+3)/(w-3) =
(w+3)/(w-3)