Math Help - Find the Riemann sum

1. Find the Riemann sum

Here is my example
To estimate the area under the graphof f(x) = 2/x + 6 from x=2 tro x=6
Find the Riemann sum usiing right endpoints and n = 4.
R4 = ?
Find the Riemann sum using left endpoints and n= 4.
L4 = ?

Thank You,
Keith

2. Let $x_0=2,x_1=3,x_2=4,x_3=5,x_4=6$
Then
$R_4=\sum_{i=1}^4f(x_i)(x_i-x_{i-1})$

$L_4=\sum_{i=1}^4f(x_{i-1})(x_i-x_{i-1})$