Chapter 11 - 11.3 - Geometric Sequences and Series - 11.3 Exercises - Page 795: 14

$a_1=7$ $a_2=28$ $a_3=112$ $a_4=448$ $a_5=1792$

$a_n=a_1r^{n-1}$ $a_1=7,~~r=4$ $a_2=7(4)^{2-1}=7(4)^1=7(4)=28$ $a_3=7(4)^{3-1}=7(4)^2=7(16)=112$ $a_4=7(4)^{4-1}=7(4)^3=7(64)=448$ $a_5=7(4)^{5-1}=7(4)^4=7(256)=1792$