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Evaluate 137lnxxdx \int_{1}^{3} \frac{7^{\ln x}}{x} \, dx

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Q. Evaluate 137lnxxdx \int_{1}^{3} \frac{7^{\ln x}}{x} \, dx
  1. Recognize Inverse Relationship: Recognize that the natural logarithm function is the inverse of the exponential function.\newlineWe have the integral:\newline137lnxxdx\int_{1}^{3}\frac{7^{\ln x}}{x}\,dx\newlineNotice that 7lnx7^{\ln x} can be rewritten using properties of exponents and logarithms as xln7x^{\ln 7}, since alnb=blnaa^{\ln b} = b^{\ln a}.\newlineSo, the integral becomes:\newline13xln7xdx\int_{1}^{3}\frac{x^{\ln 7}}{x}\,dx
  2. Rewrite Integral with Exponents: Simplify the integrand.\newlineThe xx in the denominator cancels out one xx from the numerator, simplifying the integral to:\newline13xln71dx\int_{1}^{3}x^{\ln 7 - 1} \, dx\newlineNow, the integral is:\newline13xln71dx\int_{1}^{3}x^{\ln 7 - 1} \, dx
  3. Simplify Integrands: Integrate using the power rule for integration.\newlineThe power rule states that the integral of xnx^n is (x(n+1))/(n+1)+C(x^{(n+1)})/(n+1) + C, where n1n \neq -1.\newlineApplying the power rule, we get:\newline13x(ln71)dx=[x(ln7)ln7]\int_{1}^{3}x^{(\ln 7 - 1)} dx = \left[\frac{x^{(\ln 7)}}{\ln 7}\right] from 11 to 33
  4. Apply Power Rule: Evaluate the definite integral.\newlineWe need to evaluate the expression at the upper and lower limits of the integral and subtract:\newline[3(ln7)ln7][1(ln7)ln7][\frac{3^{(\ln 7)}}{\ln 7}] - [\frac{1^{(\ln 7)}}{\ln 7}]\newlineSince any number to the power of 00 is 11, 1(ln7)1^{(\ln 7)} is 11.\newlineSo, the evaluation becomes:\newline[3(ln7)ln7][1ln7][\frac{3^{(\ln 7)}}{\ln 7}] - [\frac{1}{\ln 7}]
  5. Evaluate Definite Integral: Calculate the final answer.\newlineWe can now compute the values:\newline[3(ln7)ln7][1ln7]=3(ln7)1ln7[\frac{3^{(\ln 7)}}{\ln 7}] - [\frac{1}{\ln 7}] = \frac{3^{(\ln 7)} - 1}{\ln 7}

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