4×2(1/2)×(19/18-5/9)-5(2/5)×5/9
4×5/2×(19/18-10/18)-27/5×5/9
10×9/18-3
10×1/2-3=5-3=2
Ответ:2
S₆ = b₁(1+q+q²+q³+q⁴+q⁵) = 2(1+3+9+27+81+243) = 2*364 = 728