Answer:
I believe the answer is: [tex]3B_i[/tex]. (Your equation should look something like this: [tex]\sum _{i=3}^5\:B_{\left(i\right)}[/tex] )
Step-by-step explanation:
[tex]1. \sum _{i=3}^5=\sum _{i=1}^5-\sum _{i=1}[/tex]
2.[tex]=\sum _{i=1}^5B_{\left(i\right)}-\sum _{i=1}^2B_{\left(i\right)}[/tex]
3.=[tex]=\sum _{i=1}^5B_{\left(i\right)}= 5B_{\left(i\right)[/tex]
4.[tex]\sum _{i=1}^2B_{\left(i\right)}= 2B_{\left(i\right)[/tex]
5.[tex]5B_{\left(i\right)}-2B_{\left(i\right)}[/tex]
6.[tex]5B_{\left(i\right)}-2B_{\left(i\right)}=3B_{\left(i\right)}[/tex]
7. The answer should be: [tex]3B_{\left(i\right)}[/tex]
Hope this helps...