a) (11c² + a³)(-a³+ 11c²); б) (0,8x + y⁴)(-0,8x - y⁴); в) (0,3с – 0,2d) (0,2d – 0,3c); г) (6x³- 4x)(-6x³- 4x).

a) \[(11c^2 + a^3)(-a^3 + 11c^2) = (11c^2 + a^3)(11c^2 - a^3) = (11c^2)^2 - (a^3)^2 = 121c^4 - a^6\]

б) \[(0.8x + y^4)(-0.8x - y^4) = -(0.8x + y^4)(0.8x + y^4) = -(0.8x + y^4)^2 = -(0.64x^2 + 1.6xy^4 + y^8) = -0.64x^2 - 1.6xy^4 - y^8\]

в) \[(0.3c - 0.2d)(0.2d - 0.3c) = -(0.3c - 0.2d)(0.3c - 0.2d) = -(0.3c - 0.2d)^2 = -(0.09c^2 - 0.12cd + 0.04d^2) = -0.09c^2 + 0.12cd - 0.04d^2\]

г) \[(6x^3 - 4x)(-6x^3 - 4x) = - (6x^3 - 4x)(6x^3 + 4x) = -((6x^3)^2 - (4x)^2) = -(36x^6 - 16x^2) = -36x^6 + 16x^2\]