The first five terms are:
-20, -10, -5, -2.5, and -1.25
Explanation:Given that:
[tex]\begin{gathered} a_1=-20 \\ a_n=0.5a_{n-1} \end{gathered}[/tex]For n = 2
[tex]\begin{gathered} a_2=0.5a_1 \\ =0.5\times20 \\ =-10 \end{gathered}[/tex]For n = 3
[tex]\begin{gathered} a_3=0.5a_2 \\ =0.5\times10 \\ =-5 \end{gathered}[/tex]For n = 4
[tex]\begin{gathered} a_4=0.5a_3 \\ =0.5\times5 \\ =-2.5 \end{gathered}[/tex]For n = 5
[tex]\begin{gathered} a_5=0.5a_4 \\ =0.5\times2.5 \\ =-1.25 \end{gathered}[/tex]Therefore, the first five terms are:
-20, -10, -5, -2.5, and -1.25
