Introduction to the function

Question

If f(x+1)-f(x)=2x+1,find the value of f(3)-f(1).

Answer 1

f(3) - f(1) = [f(3) - f(2)] + [f(2) - f(1))

= [2(2)+1] + [2(1)+1] = 5 + 3 = 8