Answer
The sum of the sequence = -30072
Step-by-step explanation
We are given a sequence of numbers and asked to find the sum of the terms up until the last term given. The sequence given is
9, 4, -1,.............., -546
On careful observation of this sequence, we can see that it is an arithmetic progression with a common difference of -5 between consecutive terms.
Common difference = (n + 1)th term - nth term
= 4 - 9 Or -1 - 4
= -5
For an arithmetic progression, the formula for the last term is given as
Last term = a + (n - 1)d
where
L = last term = -546
a = first term = 9
n = number of terms in the sequence = ?
d = common difference = -5
So, we can solve for the number of terms
-546 = 9 + (n - 1)(-5)
-546 = 9 - 5n + 5
-546 = 14 - 5n
14 - 5n = -546
-5n = -546 - 14
-5n = -560
Divide both sides by -5
(-5n/-5) = (-560/-5)
n = 112
We can now use the formula for the sum of an arithmetic progression to find the sum of this sequence.
We know all of these parameters now
Sum of this AP = (112/2) [(2 × 9) + (112 - 1)(-5)]
= 56 [18 + (111 × -5)]
= 56 [18 - 555]
= 56 [ -537]
= -30072
Hope this Helps!!!