Hello!
I believe the answer is:
-9 (x - 13/3) (x + 13/3)
"Why?"
1. Do a little rearranging, as if you were rearranging your room until it looked the way you wanted it to!
169 - 9x^2 changes to: -9^2 + 169
2. From then you can factor the leading coefficient out.
-9 (x^2 + 169/9)
3. Now we will replace some numbers (169/9 with (13/3)^2), as if replacing a furniture in your room after arranging it.
-9 (x^2 + 169/9) changes to: -9 (x^2 + (13/3)^2)
4. Now, let's end this with a bang, or in this case, the difference of squares formula. (a^2 − b^2 = ( a + b ) ( a − b ) )
-9 (x - 13/3) (x + 13/3)
I apologize if this is incorrect and I hope you have an amazing day, and good luck on your studies, you can do it! :)