Nghĩ hoài mà không ra :(

N

nguyenbahiep1

[laTEX]t = x +\sqrt{a^2+x^2} \Rightarrow dt = (1 + \frac{x}{\sqrt{a^2+x^2}})dx \\ \\ dt = \frac{x +\sqrt{a^2+x^2}}{\sqrt{a^2+x^2}}dx \\ \\ dt = \frac{t}{\sqrt{a^2+x^2}}dx \\ \\ \frac{dt}{t} = \frac{1}{\sqrt{a^2+x^2}}dx \\ \\ I = ln|t| = ln|x+\sqrt{a^2+x^2}| + C[/laTEX]
 
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