Answer:
The sum of the first 70 terms of the sequence [tex]-6, -3,0,3,6, ...[/tex] is 6825.
Step-by-step explanation:
A sequence is a set of numbers that are in order.
In an Arithmetic Sequence the difference between one term and the next is a constant.
[tex]-6, -3,0,3,6, ...[/tex] This sequence has a difference of 3 between each number.
The sum of an arithmetic series is found by multiplying the number of terms times the average of the first and last terms.
[tex]S_n=\frac{n}{2}(2a_1+(n-1)d)[/tex]
where [tex]n[/tex] = the number of terms, [tex]a_1[/tex] = the first term, and [tex]d[/tex] = the common difference.
For our arithmetic sequence, the values of a, d and n are:
- [tex]a_1 =-6[/tex]
- [tex]d=3[/tex]
- [tex]n = 70[/tex]
So:
[tex]S_{70}=\frac{70}{2}(2(-6)+(70-1)3)\\\\S_{70}=35\left(3\left(70-1\right)-2\cdot \:6\right)=35\left(207-12\right)=35\cdot \:195)=6825[/tex]
