Question 948066
 20,10,0,...
<pre>

It's just a matter of plugging in the formula for the nth term:

{{{a[n]=a[1]+(n-1)d}}}

first term = a<sub>1</sub> = 20, common difference d = 10-20 = 0-10 = -10

{{{a[89]=20+(89-1)(-10)=20+(88)(-10)= -860}}}

Edwin</pre>