If you are working on arithmetic sequence, I assume you know this equation.
x = a + d(n-1)
Okay, so the first thing to do is to find the common difference.
-253 = 3 + d(33-1)
Solve for "d" and you get
d = -8
Next, I also assume you know the equation for the sum of an arithmetic sequence.
(n/2)(2a + (n-1)d)
So, plug the numbers in the equation and...
sum = (33/2)(2 x 3 - 8(33-1))
sum = -4125
Find the sum of the first 33 terms of the arithmetic sequence whose first term is 3 and whose 33rd term is -253.
2 answers
given:
a = 3
term(33) = a+32d = -253
32d = -256
d = -8
sum(33) = (33/2)(first + last)
= (33/2)(3 -253) = -4125
a = 3
term(33) = a+32d = -253
32d = -256
d = -8
sum(33) = (33/2)(first + last)
= (33/2)(3 -253) = -4125