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sbhatnagar
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Challenge Problem: For any natural number $m$, evaluate
\[\int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{1/m}dx \ \quad \ x>0\]
\[\int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{1/m}dx \ \quad \ x>0\]
sbhatnagar said:Challenge Problem: For any natural number $m$, evaluate
\[\int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{1/m}dx \ \quad \ x>0\]
Sudharaka said:Let, \(x=u^{\frac{1}{m}}\). Then the integral becomes,
\begin{eqnarray}
\int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{\frac{1}{m}}\,dx&=&\int u(u^2+u+1)(2u^2+3u+6)^{\frac{1}{m}}\,\frac{du}{mu^{1-\frac{1}{m}}}\\
&=&\frac{1}{m}\int u^{\frac{1}{m}}(u^2+u+1)(2u^2+3u+6)^{\frac{1}{m}}du\\
&=&\frac{1}{6m}\int (2u^3+3u^2+6u)^{\frac{1}{m}}\frac{d}{du}(2u^2+3u+6)\, du\\
&=&\frac{1}{6m}\frac{(2u^3+3u^2+6u)^{\frac{1}{m}+1}}{\frac{1}{m}+1}+C\\
&=&\frac{x^{m+1}(2x^{2m}+3x^m+6)^{1+\frac{1}{m}}}{6(m+1)}+C\\
\therefore \int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{\frac{1}{m}}\,dx&=&\frac{x^{m+1}(2x^{2m}+3x^m+6)^{1+\frac{1}{m}}}{6(m+1)}+C\mbox{ for }m\in\mathbb{Z^{+}}
\end{eqnarray}
Kind Regards,
Sudharaka.
Sudharaka said:Let, \(x=u^{\frac{1}{m}}\). Then the integral becomes,
\begin{eqnarray}
\int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{\frac{1}{m}}\,dx&=&\int u(u^2+u+1)(2u^2+3u+6)^{\frac{1}{m}}\,\frac{du}{mu^{1-\frac{1}{m}}}\\
&=&\frac{1}{m}\int u^{\frac{1}{m}}(u^2+u+1)(2u^2+3u+6)^{\frac{1}{m}}du\\
&=&\frac{1}{6m}\int (2u^3+3u^2+6u)^{\frac{1}{m}}\frac{d}{du}(2u^2+3u+6)\, du\\
&=&\frac{1}{6m}\frac{(2u^3+3u^2+6u)^{\frac{1}{m}+1}}{\frac{1}{m}+1}+C\\
&=&\frac{x^{m+1}(2x^{2m}+3x^m+6)^{1+\frac{1}{m}}}{6(m+1)}+C\\
\therefore \int (x^{3m}+x^{2m}+x^m)(2x^{2m}+3x^{m}+6)^{\frac{1}{m}}\,dx&=&\frac{x^{m+1}(2x^{2m}+3x^m+6)^{1+\frac{1}{m}}}{6(m+1)}+C\mbox{ for }m\in\mathbb{Z^{+}}
\end{eqnarray}
Kind Regards,
Sudharaka.
An integral is a mathematical concept that represents the area under a curve in a graph. It is used to calculate the total value of a function over a given range.
A natural number is a positive integer that is greater than or equal to 1. It is a number that is used for counting and does not include fractions or decimals.
To evaluate an integral, you need to first find the antiderivative of the function. Then, you plug in the upper and lower limits of the range into the antiderivative and subtract the result to get the final value.
The concept of integral is important because it allows us to calculate various properties of functions such as the area, volume, and average value. It is also used in many real-life applications, such as in physics, engineering, and economics.
Yes, an example of evaluating an integral for a natural number would be finding the area under the curve of the function f(x) = x^2 from x = 1 to x = 3. The integral would be calculated as follows: ∫(1 to 3) x^2 dx = [x^3/3] (1 to 3) = (3^3/3) - (1^3/3) = 9 - 1 = 8.