2) y^2-64

4) (a-2/3b)^2

6) 16/225n^2-m^2

8) -12b-16a+9b^2+12ab

10) 9/49d^2-25/16d^2

12) 1/81b^2-1/25a^2

2) (8-b)*(8+b)

4) (17/10-d)*(17/10+d)

6) (10/11-y)*(10/11+y)

8) (t-20/21)*(t+20/21)

10) (7y-4)*(7y+4)

12) 4/25*(t-15)*(t+15)