Tính đạo hàm của các hàm số cho ở bài tập 2.32
a) \(y = {\log _8}({x^2} - 3x - 4)\)
b) \(y = {\log _{\sqrt 3 }}( - {x^2} + 5x + 6)\)
c) \(y = {\log _{0,7}}\frac{{{x^2} - 9}}{{x - 5}}\)
d) \(y = {\log _{\frac{1}{3}}}\frac{{x - 4}}{{x + 4}}\)
e) \(y = {\log _\pi }({2^x} - 2)\)
f) \(y = {\log _3}({3^{x - 1}} - 9)\)
a) \({\left[ {{{\log }_8}\left( {{x^2} - 3x - 4} \right)} \right]^\prime } = \frac{{2x - 3}}{{\left( {{x^2} - 3x - 4} \right)\ln 8}}\)
b) \({\left[ {{{\log }_{\sqrt 3 }}\left( { - {x^2} + 5x + 6} \right)} \right]^\prime } = \frac{{ - 2x + 5}}{{\left( { - {x^2} + 5x + 6} \right)\ln \sqrt 3 }}\)
c)
\({\left( {{{\log }_{0,7}}\frac{{{x^2} - 9}}{{x + 5}}} \right)^\prime } = \frac{{\frac{{2x\left( {x + 5} \right) - \left( {{x^2} - 9} \right)}}{{{{\left( {x + 5} \right)}^2}}}}}{{\left( {\frac{{{x^2} - 9}}{{x + 5}}} \right)\ln \left( {0,7} \right)}} = \frac{{{x^2} + 10x + 9}}{{\left( {x + 5} \right)\left( {{x^2} - 9} \right)\ln \left( {0,7} \right)}}\)
d) \({\left( {{{\log }_{\frac{1}{3}}}\frac{{x - 4}}{{x + 4}}} \right)^\prime } = \frac{{\frac{8}{{{{\left( {x + 4} \right)}^2}}}}}{{\frac{{x - 4}}{{x + 4}}\ln \frac{1}{3}}} = \frac{8}{{\left( {{x^2} - 16} \right)\ln 3}}\)
e) \({\left[ {{{\log }_\pi }\left( {{2^x} - 2} \right)} \right]^\prime } = \frac{{{2^x}\ln 2}}{{\left( {{2^x} - 2} \right)\ln \pi }}\)
f) \({\left[ {{{\log }_3}\left( {{3^{x - 1}} - 9} \right)} \right]^\prime } = \frac{{{3^{x - 1}}\ln 3}}{{\left( {{3^{x - 1}} - 9} \right)\ln 3}} = \frac{{{3^{x - 1}}}}{{{3^{x - 1}} - 9}}\)
-- Mod Toán 12
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