# Thread: Lsub3 and Usub3 for function

1. ## Lsub3 and Usub3 for function

Find L3(f) and U3(f) for the function f(x) =1/(x+1)and the interval
[a,b] = [0,3].

2. ## Re: Lsub3 and Usub3 for function

Originally Posted by chizmin10
Find L3(f) and U3(f) for the function f(x) =1/(x+1)and the interval [a,b] = [0,3].

Please define $L_3(f)~\&~U_3(f)$. Please give an exact definition.

3. ## Re: Lsub3 and Usub3 for function

The U is the n-th upper sum for f and the L is the n-th lower sum for f.

4. ## Re: Lsub3 and Usub3 for function

Originally Posted by chizmin10
The U is the n-th upper sum for f and the L is the n-th lower sum for f.
Draw a graph. You will see that the function is decreasing on $[0,3]$.

That means that an upper sum is a left-hand sum and a lower sum is a right-hand sum.

Because $n=3$ we have $\Delta x=1$.