Question

Question below


What is the partial sum?

Answer 1

\[\sum_{i=3}^{28}3+6i\]

Answer 2

split the sum, pull the constants, then work the variable formula

Answer 3

starting i at 1 is usually helpful in determining a count ... -2 the index and +2 the rule

Answer 4

\[\Large \sum_{i=3}^{28}3+6i\]
\[\Large \sum_{i=3-2}^{28-2}3+6(i+2)\]
\[\Large \sum_{i=1}^{26}3+6i+12\]
\[\Large \sum_{i=1}^{26}15+6i\]
\[\Large \sum_{i=1}^{26}15+\sum_{i=1}^{26}6i\]
\[\Large 15(26)+6\sum_{i=1}^{26}i\]

Answer 5

Oh okay, would that leave me with 249 in the end?

Answer 6

maybe:

15(26) + 6(26)(27)/2

Answer 7

249__

missing a digit

Answer 8

216

249

282

312

These are the answers i have only triple digits

Answer 9

http://www.wolframalpha.com/input/?i=sum+%283%2B6n%29%2C+n%3D3+to+28

Answer 10

Oh, wow, it had been 8 not twenty eight sorry got them confused

Answer 11

lol, fine

15(6) + 6(6)(7)/2

Answer 12

\[\sum_{i=3}^{28}=3+6i = 3+6\times 3 + 3+6\times 4 + 3+6\times 5....3+6\times 28\]
\[\sum_{i=3}^{28}=3+6i = 21 + 27 +33+....+171\]
Here first trm a= 21
common difference d= 27-21=33-27=6 so this is an a sequence which is an A.P. ( Asthmatic Progression)
tn= 171
since
tn= a+(n-1)d
171=21+(n-1)6
171=21+6n-6
171=15+6n
171-15= 6n
156= 6n
n= 156/6
n=26

Now using sum formula
\[S_n = \frac{n}{2}(a+t_n) \]
\[S_{26}= \frac{26}{2}(21+171) = 13(21+171)= 13 \times 192 =2496\]