Ai giải giúp mình câu 6 vs 7 ạ

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Ai giải giúp mình câu 6 vs 7 ạ
ai-giai-giup-minh-cau-6-vs-7-a

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Gerda 5 years 2021-05-17T08:47:58+00:00 1 Answers 23 views 0

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  1. Thunguyet
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    2021-05-17T08:49:46+00:00
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    $6)\cos x-1=-\dfrac{x^2}{2!}+\dfrac{x^4}{4!}+o(x^4)\\ \ln\cos x=\ln(\cos x-1+1)\\ =\cos x-1-\dfrac{(\cos x-1)^2}{2}+\dfrac{(\cos x-1)^3}{3}-\dfrac{(\cos x-1)^4}{4}+o(x^4)\\ =-\dfrac{x^2}{2!}+\dfrac{x^4}{4!}-\dfrac{\left(-\dfrac{x^2}{2!}\right)^2}{2}+o(x^4)\\ =-\dfrac{x^2}{2!}-\dfrac{x^4}{12}+o(x^4)\\ 7)x\cos x=x\left(1-\dfrac{x^2}{2!}+o(x^2)\right)=x-\dfrac{x^3}{2!}+o(x^3)\\ e^{x\cos x}=1+x\cos x+\dfrac{(x\cos x)^2}{2!}+\dfrac{(x\cos x)^3}{3!}+o(x^3)\\ =1+x-\dfrac{x^3}{2!}+o(x^3)$

     

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )