Question

what is the sum of the first 10 terms of the sequence defined by An=2n-3
a.7
b.17
c.80
d.82

Answer 1

what would be the 1st term?
what would be the 10th term?

Answer 2

\(\bf S_{\color{brown}{ n}}=\cfrac{{\color{brown}{ n}}}{2}(a_1+a_{\color{brown}{ n}})
\qquad
S_{\color{brown}{ 10}}=\cfrac{{\color{brown}{ 10}}}{2}(a_1+a_{\color{brown}{ 10}})
\\ \quad \\
a_1\to first\ term\\
a_{\color{brown}{ n}}\to n^{th}\ term\)