How do you find the sum of #-10-3i# from i=1 to 15?
1 Answer
Oct 5, 2016
Manually.
#color(blue)(sum_(i=1)^(15) -10-3i)#
#-sum_(i=1)^(15) 10+3i#
#= -[10+3(1) + 10 + 3(2) + 10 + 3(3) + cdots + 10 + 3(15)]#
#= -[15*10 + 3*(1+2+3+cdots+15)]#
#= -[150 + 3*((15*16)/2)]#
#= -[150 + 3*((240)/2)]#
#= -[150 + 360]#
#= color(blue)(-510)#
