Question 1164850
<pre>
Did you mean:

(-10)+(-7)+(-4)+(-1)+(2)+(5)+(8)+(11)+(14)+(17)+(20)

with plus signs between?

If so, find the general formula for the arithmetic sequence with

{{{a[1]=-10}}}{{{and}}}{{{d=3}}}

by substituting in:

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

{{{a[n]=-10+(n-1)3}}}

{{{a[n]=-10+3n-3}}}

{{{a[n]=3n-13}}}

Then summing that from 1 to 11, since there are 11 terms:

{{{sum((3n-13),n=1,11)}}}

Edwin</pre>