ПОВТОРЕННЯ НАВЧАЛЬНОГО МАТЕРІАЛУ » §.3 (3.2)

2. b1 + b2 = 18; b1 + b3 = 30; b1 – ? b1(1 + q) = 18; b1(1 + q2) = 30; (1+q)/(1+ q^2 ) = 18/30; (1+q)/(1+ q^2 ) = 3/5; 5 + 5q = 3 + 3q2; 3q2 – 5q – 2 = 0; D = 25 + 4 • 3 • 2 = 49; q1 = (5+7)/6 = 2; q2 = (5-7)/6 = –1/3; b1 = 18/(1+q) = 18/3 = 6; b1 = 181/(1- 1/3) = 18/(2/3) = (18 •3)/2 = 27.