a1= [1 +(-1)^1 ]/2 =0
a2 = [ 1+(-1)^2 ]/2= 1
a3 = [1 + (-1)^3 ] /2 = 0
a4 = [ 1+(-1)^4 ]/2 =1
a5 = [ 1+(-1)^5 ] /2 =0
b1 =(-1)^1 x7 +1/1 = -7 +1= -6
b2 =(-1)^2 x7 +1/2 = 7+1/2 =15/2
b3 =(-1)^3 x7 +1/3 =-7 +1/3 = -20/3
b4 = (-1)^4 x7 +1/4 =7 +1/4 =29/4
b5 = (-1)^5 x7 +1/5 = -7 +1/5 =-34/5