Question 472774
-10, 20, -40, 80 a geometric progression
{{{a1=-10}}}
{{{r=a2/a1=20/(-10)=-2}}}
Formula {{{an=a1*r^(n-1)}}}
the 11th term {{{a11=a1*r^(11-1)=-10*(-2)^10=-10*1024=-10240}}}