Question

Due tomorrow. Please help!!!!

Answer 1

The common difference can be found from
$d=\dfrac{a_{17}-a_{7}}{17-7}=\dfrac{81-41}{17-7}=\dfrac{40}{10}=4$
The first term of the sequence can be found from either of the given terms.
$a_{7}=41=a_{1}+(7-1)d=a_{1}+24\\a_{1}=41-24=17$

The sum of 40 terms is
$S_{40}=\dfrac{40}{2}(a_{1}+a_{40})=20(17+(17+39\cdot 4)=20\cdot 190=3800$

The sum of the first 40 terms is 3800.