Answer:
All but the fourth
Step-by-step explanation:
The fourth is a sum (+) not difference (-).
All others are some form of difference of squares:
[tex]169x^4-49 = \left(13x^2\right)^2-7^2[/tex]
difference of square of number 13x² and square of number 7
[tex]36-25b^2=6^2-(5b)^2[/tex]
difference of square of number 6 and square of number 5b
[tex]100-r^2=10^2-r^2[/tex]
difference of square of number 10 and square of number r
[tex]64y^2-81=(8y)^2-9^2[/tex]
difference of square of number 8y and square of number 9
