Cho hàm số f(x) = log5(x2 + 1). Khi đó:
(A) \(f'(1) = \frac{1}{{2\ln 5}}\)
(B) \(f'(1) = \frac{1}{{\ln 5}}\)
(C) \(f'(1) = \frac{3}{{2\ln 5}}\)
(D) \(f'(1) = \frac{2}{{\ln 5}}\)
Ta có:
\(f'(x) = \frac{{2x}}{{{x^2} + 1}}.\frac{1}{{\ln 5}} \Rightarrow f'(1) = \frac{1}{{\ln 5}}\)
Chọn (B).
-- Mod Toán 12
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