Question

Please evaluate the equation​

Answer 1

Step-by-step explanation:

$= \sum \limits_{n = 1}^{7} ( - 2. {6}^{n - 1} )$

$= \sum \limits_ {n = 1}^{n_{ \text{max}}} (a_1. {r}^{n - 1} )$

$\:$

$a_1 = - 2$

$n = 7$

$r = 6 \to r >1$

$\:$

• Find S7.

$s_n = a_1.( \frac{ {r}^{n} - 1}{r - n} )$

$s_7 = - 2.( \frac{ {6}^{7} - 1 }{6 - 1} )$

$s_7 = - 2.( \frac{279.936 - 1}{5} )$

$s_7 = - 2.( \frac{279.935}{5} )$

$s_7 = - 2 \: . \: 55.987$

$s_7 = - 111.974$

The answer is B.