Question 585320
a1 = 10, r =-1

nth term of a geometric sequence is given by:   {{{ xn = a1*r^(n-1) }}}

So,  a2 = a1*r^(2-1) = a1*r = 10*(-1) = -10
     a3 = a1*r^(3-1) = a1*r^2 = 10*(-1)^2 = 10*1 = 10
     a4 = a1*r^(4-1) = a1*r^3 = 10*(-1)^3 = 10*(-1) = -10
     a5 = a1*r^(5-1) = a1*r^4 = 10*(-1)^4 = 10*1 = 10

Hope this helps~!