Question 380157
Find the sum of the first n terms of the following arithmetic sequence.

a1 = 2, d = 2; n = 5. 
 Sol'n:
  
 S = n/2[2a1+(n-1)d]
   = (5/2)[2(2)+(5-1)2]
   = (5/2)[4+8]
   = (5/2)(12)
 S = 30 --answer