Answer and Step-by-step explanation:
The formula for an arithmetic sequence is:
[tex]a_{n} = a_{1} + (n-1)d[/tex]
Plug in the given values.
[tex]a_{11} = 2.5 + (11 -1)(1.5)\\\\a_{11}=2.5 + (10)(1.5)\\\\a_{11} = 2.5 + 15\\\\a_{11}=4[/tex]
The formula for the sum on an arithmetic sequence is:
[tex]S_{n} = \frac{n(a_1+a_n)}{2}[/tex]
Plug in the values.
[tex]S_{11} = \frac{11(2.5 + 4)}{2} = 35.75[/tex]
#teamtrees #PAW (Plant And Water)
I hope this helps!
