To calculate the area for the upper (left) graph, we can use x = 1, 2, 3 and 4 to find the upper limit of each rectangle:
[tex]\begin{gathered} f(1)=\frac{3}{1}+3=6\\ \\ f(2)=\frac{3}{2}+3=4.5\\ \\ f(3)=\frac{3}{3}+3=4\\ \\ f(4)=\frac{3}{4}+3=3.75 \end{gathered}[/tex]
Since the x-interval of each rectangle is 1 unit, the area of each rectangle is given by its y-value, so we have:
[tex]\begin{gathered} A=f(1)+f(2)+f(3)+f(4)\\ \\ A=6+4.5+4+3.75=18.25 \end{gathered}[/tex]
Now, for the bottom (right) graph, the limits of the rectangles are x = 2, 3, 4 and 5.
So, let's find the value of f(5):
[tex]f(5)=\frac{3}{5}+3=3.6[/tex]
So the area is given by:
[tex]\begin{gathered} A=f(2)+f(3)+f(4)+f(5)\\ \\ A=4.5+4+3.75+3.6=15.85 \end{gathered}[/tex]
