Question

СРОЧНО!!!!!! Помогите пожалуйсто!

Answer 1

b3=b1.qˇ2, b1=2/9:1/9 = 2, b1=2
b2=b1.q=2.1/3=2/3
b1+b2+b3 = 2+2/3 +2/9=18/9+6/9+2/9 = 26/9

Answer 2

b₃=2/9;q=1/3;⇒
b₃=b₁q²;⇒b₁=b₃/q²=2/9:1/9=2;
Sn=b₁(1-qⁿ)/(1-q);
S₃=b₁(1-q³)/(1-q)=2(1-1/27)/(1-1/3)=2· (26/27)/(2/3)=2·26·3/(27·2)=
=26/9=2⁸/₉;