B2 = b1q 9 = b1q
b4 = b1q^3 16=b1q^3 разделим 2-е уравнение на 1-е, получим: q^2 = 16/9, q= +-4/3
а)q = 4/3 9 = b1q, 9 = b1*4/3, b1 = 9:4/3 = 9 * 3/4= 27/4, b6 = b1q^5 = 27/4*(4/3)^5= 256/9
б) q = -4/3 9 = b1q, 9 = b1*(-4/3), b1 = 9:(-4/3) = 9*(-3/4) = -27/4, b6 = b1*q^5 =- 27/4 *(-4/3)^5=256/9