function f(x)
   return x^2 + 2*x + 3 
end

N = 100
a, b = 0, 2

h = ( b - a ) / N
sum = f(a) + f(b)
x = a
for i = 1, N-1 do
   x = x + h
   sum = sum + 2 * f(x)
end
T = sum * h / 2
io.write( "\nTrapezoid rule result: ", T, "\n\n" )