Answer:
Summation: [tex]\sum_{n=1}^4(3n+12)[/tex]
Explicit formula: [tex]a_n=3n+12[/tex]
Step-by-step explanation:
The given series is 15 + 18 + 21 + 24.
The first term of this series is [tex]a_1=15[/tex].
The common difference is [tex]d=18-15=3[/tex]
The explicit formula is given by: [tex]a_n=a_1+d(n-1)[/tex].
We plug in the known values to get:
[tex]a_n=15+3(n-1)[/tex]
[tex]a_n=15+3n-3[/tex]
The explicit formula is [tex]a_n=3n+12[/tex]
The summation that represents the series is: [tex]\sum_{n=1}^4(3n+12)[/tex]
