Decompose integrand into partial fractions: We need to decompose the integrand into partial fractions. To do this, we set up the equation:(x−2)(x2+x+1)1=x−2A+x2+x+1Bx+CWe will find the values of A, B, and C that make this equation true.
Clear fractions by multiplying: Multiply both sides of the equation by the denominator (x−2)(x2+x+1) to clear the fractions:1=A(x2+x+1)+(Bx+C)(x−2)Now we will find A, B, and C by comparing coefficients or plugging in suitable values for x.
Find values of A, B, and C: Let's plug in x=2 to find A, since that will eliminate the terms with B and C:1=A(22+2+1)1=A(7)A=71
Find A by plugging in x=2: To find B and C, we can either compare coefficients or choose other values for x. Let's choose x=0 to find C: 1=A(02+0+1)+C(0−2) 1=(1/7)(1)−2C 1=1/7−2C x=20 x=21 x=22
Find C by plugging in x=0: Now we need to find B. We can compare coefficients for the x term. The coefficient of x on the left side is 0, and on the right side, it is A+B−2C. We already know A and C, so we can solve for B: 0=A+B−2C 0=71+B+76 x0
Find B by comparing coefficients: Now that we have A, B, and C, we can write the integral as:∫(x−2)(x2+x+1)1dx=∫71(x−2)1dx+∫7−x−3(x2+x+1)1dxWe will integrate each term separately.
Write integral with A, B, and C: Integrate the first term: ∫71÷(x−2)dx=71ln∣x−2∣+C1
Integrate first term: For the second term, we need to complete the square for the denominator x2+x+1:x2+x+1=(x+21)2+43Now we can rewrite the integral as:∫x2+x+1−x−73dx=∫(x+21)2+43−x−73dx
Complete the square for the denominator: We can split the second integral into two parts: \int\frac{-x-\frac{\(3\)}{\(7\)}}{(x+\frac{\(1\)}{\(2\)})^\(2\) + \frac{\(3\)}{\(4\)}}dx = \int\frac{-x}{(x+\frac{\(1\)}{\(2\)})^\(2\) + \frac{\(3\)}{\(4\)}}dx + \int\frac{-\frac{\(3\)}{\(7\)}}{(x+\frac{\(1\)}{\(2\)})^\(2\) + \frac{\(3\)}{\(4\)}}dx
Split second integral into two parts: Integrate the first part of the second term using substitution:\(\newlineLet u=x+21, then du=dx, and the integral becomes:∫u2+43−uduThis is the integral of the form u2+a2−u, which can be integrated as −21ln(u2+a2)+C2.
Integrate first part using substitution: Integrate the second part of the second term using a trigonometric substitution:Let u=x+21, and a2=43. Then the integral becomes:∫7−3(u2+(3/2)21)duThis is the integral of the form u2+a2a, which can be integrated as −aarctan(au)+C3.
Integrate second part using trigonometric substitution: Combine the results from steps 7, 10, and 11: \int \frac{\(1\)}{(x\(-2\))(x^\(2\)+x+\(1\))}\,dx = \frac{\(1\)}{\(7\)}\ln|x\(-2| - \frac{1}{2} \ln\left((x+\frac{1}{2})^2 + \frac{3}{4}\right) - \frac{3}{7} \arctan\left(\frac{2}{\sqrt{3}}(x+\frac{1}{2})\right) + C
Combine results from steps 7, 10, and 11: Simplify the final answer by combining the constants:∫(x−2)(x2+x+1)1dx=71ln∣x−2∣−21ln((x+21)2+43)−73arctan(32(x+21))+CWhere C is the constant of integration.
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