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)=

1)(0.2a-0.5b)(0.2a+0.5b)= 0.04а²-0.25b²
2)(0.1x³-0.3y)(0.1x³+0.3y)=0.01x^9-0.09y²
3)(a²-b²)(a²+b²)=a⁴-b⁴