1)(0.2a-0.5b)(0.2a+0.5b)= 2)(0.1x^3-0.3y)(0.1x^3-0.3y)= 3)(a^2-b^2)(a^2+b^2)= 4)(x^3+y^3)(x^3-y^3)=

1)(0.2a-0.5b)(0.2a+0.5b)= (0.2a)^2 - (0.5b)^2 = 0.04a^2 - 0.25b^22)(0.1x^3-0.3y)(0.1x^3-0.3y)= (0.1x^3)^2 - (0.3y)^2 = 0.01x^6 - 0.09y^2 3)(a^2-b^2)(a^2+b^2)=(a^2)^2 - (b^2)^2 = a^4 - b^44)(x^3+y^3)(x^3-y^3)=x^6-y^6