Answer:
[tex]\large\boxed{\sum\limits_{n=1}^5(-2.2+8.8n)}[/tex]
Step-by-step explanation:
[tex]6.6,\ 15.4,\ 24.2,\ ...\\\\\text{It's an arithmetic sequence:}\\\\15.4-6.6=8.8\\24.2-15.4=8.8\\\\\text{The difference is constant.}\\\\\text{The explicit formula of an arithmetic sequence:}\\\\a_n=a_1+(n-1)d\\\\\text{Substitute:}\\\\a_1=6.6\ \text{and}\ d=8.8\\\\a_n=6.6+(n-1)(8.8)=6.6+8.8n-8.8=8.8n-2.2\\\\\text{Therefore}\\\\\sum\limits_{n=1}^5(8.8n-2.2)[/tex]
