Question 930941
<pre>
{{{a[1]=9}}}, {{{a[2]=2}}}

{{{d=a[2]-a[1]=2-9=-7}}}

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

{{{a[25]=9+(25-1)(-7)}}}

{{{a[25]=9+(24)(-7)}}}

{{{a[25]=9+(-168)}}}

{{{a[25]=-159}}}

Checking:

   9,    2,   -5,  -12,  -19, -26,  -33,  -40,  -47,  -54, 
 -61,  -68,  -75,  -82,  -89, -96, -103, -110, -117, -124,
-131, -138, -145, -152, -159. 

Edwin</pre>