Question 1063220
<pre<b>
{{{matrix(1,20,

common, 
ratio,
""="",
matrix(1,2,2nd,term)/matrix(1,2,1st,term),
""="",
(5x^7)/(5x^6),
""="",
x,
""="",
matrix(1,2,3rd,term)/matrix(1,2,2nd,term),
""="",
5x^8/(5x^7),
""="",
x,
""="",
matrix(1,2,4th,term)/matrix(1,2,3rd,term),
""="",
5x^9/(5x^8),
""="",
x)}}}

{{{matrix(1,13,

The, 
formula, 
is, 
S[infinity]=a[1]/(1-r),
",",
where,
a[1]=5x^6,
and,
r=x,
so,
simply,
plug,
"in.")}}}
 
{{{matrix(1,1,Edwin)}}}</pre></b>