a)
(x-3)(x+3)=0
x=3 ∨ x=-3
b)
(3y-1)(5y+8)=0
3y-1=0
3y=1
y=1/3
5y+8=0
5y=-8
y=-8/5
a) 25x^2-30xy+9y^2+30xy = 25x^2+9y^2