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3х - 5( 2х - 1) = 3( 3 - 2х )
3х - 10х + 5 = 9 - 6х
- 7х + 6х = 9 - 5
- х = 4
х = - 4
Q=-3 S₅=-305 n=5 b₁-?
Sn=b₁(qⁿ-1)/(q-1)
b₁*((-3)⁵-1)/((-3)-1)=-305
b₁*(-243-1)/(-4)=-305
b₁*(-244/)-4)=-305
b₁=-305/61=-5
Ответ: b₁=-5.