What is the sum of the first 14 terms of the sequence -11+(-18)+(-25)+(-32)...
1 answer:
The difference between -11 and -18 is -7
the difference between -18 and -25 is <span>-7
</span>the difference between -25 and -32 is <span>-7
</span>
therefore we can say that the difference between all of the terms will be -7.
the first term is -11 -> call this a
the difference is -7 -> call this d
the number of terms is 14 -> call this <span>n
</span>
use the equation (sum of)
= 
(2a + (n-1)d)
(sum of) = 
(2 x -11 + (14-1)-7)
= -7(-22 + (13 x -7))
= -7(-22 + -91)
= -7(-111)
= 777
the difference between -18 and -25 is <span>-7
</span>the difference between -25 and -32 is <span>-7
</span>
therefore we can say that the difference between all of the terms will be -7.
the first term is -11 -> call this a
the difference is -7 -> call this d
the number of terms is 14 -> call this <span>n
</span>
use the equation (sum of)
(sum of)
= -7(-22 + (13 x -7))
= -7(-22 + -91)
= -7(-111)
= 777
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