SOLUTION: http://imageshack.us/photo/my-images/824/page679.jpg/ I need help number 11 Please!

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: http://imageshack.us/photo/my-images/824/page679.jpg/ I need help number 11 Please!      Log On


   

Question 475976: http://imageshack.us/photo/my-images/824/page679.jpg/
I need help number 11 Please!
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
sum%2814-2k%2C+k=3%2C+15%29
if k=3 a1=14-2%2A3=8
k=4 a2=14-2%2A4=6
k=5 a3=14-2%2A5=4
...
k=15 a13=14-2%2A15=-16
8, 6, 4, ... the arithmetic series
a1=8, d=-2
Use formula Sn=%28n%2F2%29%28a1%2Ban%29
n=13, a1=8, a13=-16
sum%2814-2k%2C+k=3%2C+15%29=S13=%2813%2F2%29%288%2B%28-16%29%29=-52