Question

summation from k=1 to 3 (-1)^k (k-2)^2
write the sum without the sigma notation and evaluate it. Help any1?

Answer 1

\[\sum_{k=1}^{3} (-1)^{k}(k-2)^{2}\]

Answer 2

where are you stuck?

Answer 3

\[(-1)^{1}(1-2)^{2} + (-1)^{3}(3+2)^{3}\]

Answer 4

ive tried pluggin in the 1 and the 3

Answer 5

dunno if im right

Answer 6

where is k =2?

Answer 7

ok,
k =1, then the expression is \( (-1)^1(1-2)^2= -1\), right?

Answer 8

so i have to plug in all the numbers from 1 to 3? lol thought its just 1 and 3

Answer 9

k =2 , then the expression is \((-1)^2 (2-2)^2 =0, right?

Answer 10

should be from 1 to 3

Answer 11

Yes, although k =2 makes the expression =0, you must put it in to show that it is there but =0

Answer 12

but you calculate k =3 is wrong.

Answer 13

how?

Answer 14

it is \((-1)^3 (3-2)^2=-1\)

Answer 15

you let (3+2) ^2 not 3-2

Answer 16

ahaha ye

Answer 17

so all of that equals to = -2

Answer 18

yup

Answer 19

thank you very much, have a nice day