1) = 27a^3 +3*9a^2 +3*3a + 1 = 29a^3 + 27a^2 + 9a + 1
2) = [(1+a)-a^2]^2= (1+a)^2 - 2(1+a)*a^2 + a^4 = 1+2a+a^2-2a^2-2a^3 + a^4 =
a^4 -2a^3 - a^2 + 2a + 1
3) = (a+b)^2 - c^2 = a^2 + b^2 -c^2 +2ab Ai ci am folosit formula (x+y)(x-y)=x^2 - y^2, unde x= a+b si y=c.
