Question 531417
Solving by FOIL method 

(3a-2b) (3a+2b)
 
(3a* 3a)+ (3a * 2b) - (2b * 3a) + (-2b * 2b)
  9a^2  +     6ab   -     6ab   -     4b^2 

= 9a^2 - 4b^2