Question

http://prntscr.com/ami1ib help please

Answer 1

@imqwerty

Answer 2

there is no parenthesis so I will consider this question as sum of 2i from 7 to 16 then from the result subtract 12. Now \[\sum2i\] is equal to \[2 \sum i\] then it follows 2(-i+1+i-1-i+1+i-1-i+1) - 12 = 2(-i+1) -12= -2i -10

Answer 3

Uhh I'm a little confused :s

Answer 4

If you like to find a result something like in the choices, you can do same process doing \[\sum(2i-12)\] I just think choices or question is wrong since it should include i as well. If there is something else confusing you I wish I can help.

Answer 5

\[sum_{i=7}^{16}2i-12\]

now we will try to write this summation series in "expanded form"

so it will go like this-

\[sum_{i=7}^{16}2i-12=\underbrace{\left[2(7)-12\right]+\left[2(8)-12\right]+\left[2(9)-12\right]+....+\left[2(16)-12\right]}\]
there are 10 terms and each term has one "-12" so there are ten -12s.

we just put them together

we get this-

\[sum_{i=7}^{16}2i-12=\underbrace{2(7)+2(8)+2(9)+...2(16)}+10\left[-12\right]\]
this part is a geometric progression try to solve it

Answer 6

I'm really sorry both of you... These days we see so much imaginary number and I confused it here. sorry Hayhayz and thanks imqwerty

Answer 7

=110! and its all good @sumeer :) Thanks qwerty

Answer 8

:) np