а) (a+1)^2 - 2(a+1) + 1 = a^2 + 2a + 1 - 2a - 2 + 1 = a^2 - 1
б) (x+2y)^2 + 2(x^2 - 4y^2) + (2y-x)^2 = x^2 + 4xy + 4y^2 + 2x^2 - 8y^2 + 4y^2 - 4xy + x^2 - 4y + 4y^2 - 4x + 4xy + x^2 = 4x^2 + 12y^2
а) (a+1)^2 - 2(a+1) + 1 = a^2 + 2a + 1 - 2a - 2 + 1 = a^2 - 1
б) (x+2y)^2 + 2(x^2 - 4y^2) + (2y-x)^2 = x^2 + 4xy + 4y^2 + 2x^2 - 8y^2 + 4y^2 - 4xy + x^2 - 4y + 4y^2 - 4x + 4xy + x^2 = 4x^2 + 12y^2