Question 612395
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi, 
write the following arithmetic series in sigma notation:
{5+1+(-3)+(-7)+(-11)....}  d= -4 and {{{a[n]=a[1]+(n-1)*d = 5 + (n-1)(-4) = -4n + 9}}}
{{{sum( (-4n+9), n=1, infinity )}}}
{-3,0,3,6,9,...} d= 3 and {{{a[n]=a[1]+(n-1)*d = -3 + (n-1)(3) = 3n -6}}}
{{{sum( (3n-6), n=1, infinity )}}}