d)
a_1=-4 , q=\frac{1}{2}
a_4=a_1*q^3=-4*(\frac{1}{2})^3=-4*\frac{1}{8}=-\frac{1}{2}
a_5=-\frac{1}{2}*\frac{1}{2}=-\frac{1}{4}
a_6=-\frac{1}{4}*\frac{1}{2}=-\frac{1}{8}
a_7=-\frac{1}{8}*\frac{1}{2}=-\frac{1}{16}
a_8=-\frac{1}{16}*\frac{1}{2}=-\frac{1}{32}
e)
a_2=-25 , a_3=5
a_2*q=a_3
-25*q=5
q=\frac{5}{-25}=-\frac{1}{5}
a_4=a_3*q=5*(-\frac{1}{5})=-1
a_5=-1*(-\frac{1}{5})=\frac{1}{5}
a_6=\frac{1}{5}*(-\frac{1}{5})=-\frac{1}{25}
a_7=-\frac{1}{25}*(-\frac{1}{5})=\frac{1}{125}
a_8=\frac{1}{125}*(-\frac{1}{5})=-\frac{1}{625}
f)
a_3=\frac{1}{3}
a_3*a_4=1/:a_3
a_4=\frac{1}{a_3}=\frac{1}{\frac{1}{3}}=1*3=3
a_3*q=a_4
\frac{1}{3}*q=3/*3
q=9
a_5=a_4*q=3*9=27
a_6=27*9=243
a_7=243*9=2187
a_8=2187*9=19683