Chapter 10 - Section 10.3 - Geoetric Sequences and Series - Exercise Set - Page 1074: 34

$-6564$

The general formula to find the nth partial sum of a Geometric sequence is given as: $ S_{n}=\dfrac{a(1-r^n)}{(1-r)}$ $ a_1=(4)(-3)^{1}=-12$ wen $ i=1$ Now, $ S_{7}=\dfrac{(-12) \times [1-(-3)^{7}]}{[1-(-3)]}=-12 \times (\dfrac{2188}{4})$ Our answer is: $ S_{7}=-6564$