# Thread: find an upper/lower bound for the integral

1. ## find an upper/lower bound for the integral

Hello, am a complete novice attempting an on-line course, can you show me how to work this problem? Thanks for your time.

Find an upper and lower bound for the integral $\displaystyle \int_{0}^{1}\frac{1}{x+2}dx$ using the comparison properties of integrals.

2. Originally Posted by FLTR
Hello, am a complete novice attempting an on-line course, can you show me how to work this problem? Thanks for your time.

Find an upper and lower bound for the integral $\displaystyle \int_{0}^{1}\frac{1}{x+2}dx$ using the comparison properties of integrals.
Maybe this will help, for $\displaystyle x>0$
$\displaystyle 0<\frac{1}{x+2}<\frac{1}{x}$
Then,
$\displaystyle 0<\int_0^1 \frac{dx}{x+2} < \int_{0^+}^1 \frac{dx}{x}=\ln x$

3. Hello, FLTR!

Find an upper and lower bound for the integral $\displaystyle \int_{0}^{1}\frac{1}{x+2}dx$
using the comparison properties of integrals.

Since $\displaystyle 0 \leq x \leq 1:\;\;2\:\leq \;x+2\:\leq \:3\quad\Rightarrow\quad \frac{1}{3} \,\leq \,\frac{1}{x+2} \,\leq \,\frac{1}{2}$

Hence: .$\displaystyle \int^1_0\!\frac{1}{3}\,dx \;\leq \;\int^1_0\!\!\frac{dx}{x+2} \; \leq \; \int^1_0\!\frac{1}{2}\,dx$

Therefore: .$\displaystyle \frac{1}{3} \;\leq \;\int^1_0\!\!\frac{dx}{x+2} \;\leq \;\frac{1}{2}$

4. Thanks for the examples. I should be able to work the remaining exercises, at least on this type of problem!

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### find the upper bounds and lower bound of the integral

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