MHB How Can I Use Substitution to Solve This Integral?

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$$\int\frac{2x}{x^2+9}\ \text{dx}$$
I thot I could use
$$u={x}^{2}+9$$
But counldn't go thru with it
 
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karush said:
$$\int\frac{2x}{x^2+9}\ \text{dx}$$
I thot I could use
$$u={x}^{2}+9$$
But counldn't go thru with it

(Wave)

$$u=x^2+9 \Rightarrow du=2x dx $$

$$\int\frac{2x}{x^2+9} dx=\int \frac{du}{u}=\ln |u|+c=\ln |x^2+9|+c=\ln(x^2+9)+c$$
 
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