Answer: (3+xz)(-3+xz); (y^2-xy)(y^2+xy) ; (64y^2+x^2)(-x^2+64y^2)
Explanation:
The formula for difference of squares is (a+b)(a-b)= a^2-b^2.
The first 2 don't work.
The 3rd one can be written as (3+xz)(3-xz).
The 4th and 5th can be written the same way.