Question

Дано 7, -11

Найти q, b3, b6, s5


И дано -3, 12

Answer 1

$b_1=7\; ,\; b_2=-11\; ,...\; \; \to \\\\q=\frac{b_1}{b_1}=-\frac{11}{7}\\\\b_3=b_2\cdot q=-11\cdot \frac{-11}{7}=\frac{121}{7}\\\\b_6=b_1q^5=7\cdot (-\frac{11}{7})^5=7\cdot (-\frac{11^5}{7^5})=-\frac{11^5}{7^4}=-\frac{161051}{2401}=67\frac{184}{2401}\\\\S_5=\frac{b_1\, (q^5-1)}{q-1}=\frac{7\cdot (-\frac{11^5}{7^5}-1)}{-\frac{11}{7}-1}=\frac{7\cdot \frac{-161051-16807}{7^5}}{-\frac{18}{7}}=\frac{-1777858}{-18\cdot 7^3}=287\frac{5920}{6174}$