The figure shown has a parabola with the equation y=x^2. Therefore, we can calculate the area below a parabola and above the x-axis
consider the intervals: [0, b/n], [b/n, 2b/n], [2b/n,3b/n]...[(n-1)b/n,b] In which we can separate into 7 equal intervals, in the form 0, b/7, 2b/7, 3b/7,..., b.
Let us take the rectangle based on the interval [(k − 1) · b/n, k · b/n] and height determined so that the rectangle is maximized, always remaining below of the graph of the parabola. The sum of the areas of such rectangles is called the lower sum for the
area below the parabola. This sum, denoted by s(n), provides a value that is always lower
to the exact area for any value of n.
In a similar way, we can take rectangles positioned above the parabola graph,
being characterized by the lowest possible height, resulting in a superior estimate for
the exact area. The sum of the areas of these rectangles is called the upper sum for the area
below the parabola and is denoted by S(n).
a)Consider b = 1. Find a positive integer N_1,2 > 1 such that:
S(N_1)-s(n_1)<0,01
S(N_2)-s(n_2)<0,0001
b)Based on the results obtained in the previous item, what can you conclude about the area
exact below the parabola and above the x axis between the abscissa x = 0 and x = b? So
more precise: express this area as a function of b and justify your answer.