ответ: S=8-8√2.
Объяснение:
-4√2; 4; -2√2; ...
b₁=-4√2 b₂=4
q=b₂/b₁=4/(-4√2)=-1/√2.
S=b₁/(1-q)=-4√2/(1-(-1/√2))=-4√2/(1+(1/√2))=-4√2/((√2+1)/√2))=
=-4*√2*√2/(√2+1)=4*2/(√2+1)=-8/(√2+1)=-8*(√2-1)/((√2+1)*(√2-1))=
=-8*(√2-1)/(2-1)=-8*(√2-1)=8-8√2.
ответ: S=8-8√2.
Объяснение:
-4√2; 4; -2√2; ...
b₁=-4√2 b₂=4
q=b₂/b₁=4/(-4√2)=-1/√2.
S=b₁/(1-q)=-4√2/(1-(-1/√2))=-4√2/(1+(1/√2))=-4√2/((√2+1)/√2))=
=-4*√2*√2/(√2+1)=4*2/(√2+1)=-8/(√2+1)=-8*(√2-1)/((√2+1)*(√2-1))=
=-8*(√2-1)/(2-1)=-8*(√2-1)=8-8√2.