How to Integrate 1/(1+2x+x^2) dx Without Getting Stumped

In summary, the general formula for integrating 1/(1+2x+x^2) is ∫1/(a^2+bx+c) dx = 1/(b^2-4ac) ln |(ax+b)/(a√(a^2+bx+c))| + C, where a, b, and c are constants. This integral can be solved using the substitution method, with the range of values for which it is defined being (-∞, -1) U (-1, ∞). It is convergent, as the function approaches 0 as x approaches ±∞. Additionally, it can be solved using partial fractions decomposition by decomposing 1/(1+2x+x^
  • #1
FUNKER
121
0
In an exam i stumbled when i saw this q
integrate:
1/(1+2x+x^2) dx
:grumpy:
help
 
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  • #2
[tex]\int \frac{dx}{1+2x+x^2}[/tex]

[tex]\int \frac{dx}{(1+x)^2} [/tex]

Whats the pro
 
  • #3
himanshu121 said:
[tex]\int \frac{dx}{1+2x+x^2}[/tex]

[tex]\int \frac{dx}{(1+x)^2} [/tex]

Whats the pro
?
?
 
  • #4
[tex] 1 + x^2[/tex] + [tex]\frac{1}{3}x^3[/tex]
 
Last edited:
  • #5
Substitute [itex]u=x+1[/itex]. [itex]du=dx[/itex] so we get

[tex]\int\frac{dx}{(1+x)^2}=\int\frac{du}{u^2}=\int u^{-2}du[/tex]

That should make it a little easier to see what rule you can apply.
 

1. What is the general formula for integrating 1/(1+2x+x^2)?

The general formula for integrating 1/(1+2x+x^2) is ∫1/(a^2+bx+c) dx = 1/(b^2-4ac) ln |(ax+b)/(a√(a^2+bx+c))| + C, where a, b, and c are constants.

2. Can this integral be solved using substitution?

Yes, this integral can be solved using the substitution method. Let u = 1+2x+x^2, then du/dx = 2+2x and dx = du/(2+2x). Substituting these values into the integral, we get ∫1/u du = ln|u| + C = ln|1+2x+x^2| + C.

3. What is the range of values for which this integral is defined?

This integral is defined for all real values of x, except when the denominator (1+2x+x^2) equals 0. This occurs when x = -1 ± i, where i is the imaginary unit. Therefore, the range of values for which the integral is defined is (-∞, -1) U (-1, ∞).

4. Is this integral convergent or divergent?

This integral is convergent. As x approaches ±∞, the function 1/(1+2x+x^2) approaches 0, which means the area under the curve is finite.

5. Can this integral be solved using partial fractions decomposition?

Yes, this integral can also be solved using partial fractions decomposition. The function 1/(1+2x+x^2) can be written as 1/(x+1)^2, which can be decomposed into the sum of two fractions with denominators (x+1) and (x+1)^2. The integral can then be solved by integrating each of these fractions separately.

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