1) (3а-2)(3а+2)
2) (у-5х)^2

(3а - 2)(3а + 2) = 9а^2 - 4

(у - 5х)^2 = у^2 - 10ух + 25х^2

1. (3a-2)(3a+2)=(3a)^2 -2^2= 9a^2 -4

2. (y-5x)^2=y^2 -2y*5x+(5x)^2= y^2 -10xy+25x^2