In order to find the left, the method is
1. Divide the interval [0,50] in 99 intervals.
2. Multiply the length of the first interval by the image of the left side of that interval
3. Do the same with all of them
4. Sum all the 99 results
On the right side, just changes 2. to the right side of the interval.
After that process, you will obtain that, the left sum is -9798.99, and the right sum is -10001.01.
In sigma notation, the left sum is
[tex]\sum_{i\mathop{=}0}^{99}[x_i-x_{i+1}]min(f(x_i),f(x_{i+1}))[/tex]The right sum is
[tex]\sum_{i\mathop{=}1}^{100}[x_i-x_{i+1}]max{}{}f((x_i),f(x_{i+1}))[/tex]