Question

Find the 11th partial sum of the summation of negative 7i plus 22, from i equals 1 to infinity.

∞
∑ -7+22?
i=1

Answer 1

I think you mean,


`\sum_(i=1)^(\infty)(7i+22)`

You can use the usual formula,


`S_(k)=(k)/(2)(a_1+a_k)`

That in this case is,


`S_(11)=(11)/(2)(29+99)=704`

Where I have used,


`a_k=7\cdot k +22`