Answer:
The sum of first 70 terms of the given sequence = 6825
Step-by-step explanation:
The sequence is given to be : -6, -3, 0, 3, 6, .......
Since, The common difference is same for all the terms in the sequence , so the given sequence is in A.P.
Now, finding the sum of first 70 terms of an A.P.
First term, a = -6
Number of terms, n = 70
Common difference, d = 3
[tex]Sum=\frac{n}{2}(2a+(n-1)\times d)\\\\\implies Sum=\frac{70}{2}(2\times -6+(70-1)\times 3)\\\\\implies Sum=35\times (-12+207)\\\\\implies Sum = 35\times 195\\\\\implies Sum = 6825[/tex]
Therefore, the sum of first 70 terms of the given sequence = 6825
