How do you use the properties of summation to evaluate the sum of #Sigma 2i-3# from i=1 to 15?
1 Answer
Jan 5, 2017
# sum_(i=1)^15 (2i-3) = 195 #
Explanation:
Use the standard summation formula
# sum_(r=1)^n r = 1/2n(n+1) #
# sum_(i=1)^15 (2i-3) = 2sum_(i=1)^15 i-3sum_(i=1)^15 1 #
# " " = 2*1/2(15)(16) - 3*15#
# " " = 240-45 #
# " " = 195 #
