If f(x)=a0+a1x+......, then (f(1)+f(-1))/2 =

Question

F(x)=a₀+a₁x+a₂x²+.......+a_2nx²ⁿ,then find value of (f(1)+f(-1))/2

Answer 1

Why don't you write out a few terms, say 9, of f(1) and immediately beneath it 

write out the corresponding terms of f(-1).  Then add each column of two terms, and see what happens!