Recognize Problem Complexity: Recognize that the integral of x3+11 is not a standard integral and will likely require partial fraction decomposition.
Factor Denominator: Factor the denominator x3+1. This can be factored using the sum of cubes formula: a3+b3=(a+b)(a2−ab+b2), where a=x and b=1.x3+1=(x+1)(x2−x+1)
Set Up Partial Fractions: Set up the partial fraction decomposition.x3+11=(x+1)(x2−x+1)1=x+1A+x2−x+1Bx+C
Clear Fractions: Multiply both sides by the common denominator (x+1)(x2−x+1) to clear the fractions.1=A(x2−x+1)+(Bx+C)(x+1)
Expand and Collect Terms: Expand the right side and collect like terms.1=Ax2−Ax+A+Bx2+Bx+Cx+C1=(A+B)x2+(−A+B+C)x+(A+C)
Equate Coefficients: Equate the coefficients of corresponding powers of x on both sides of the equation.For x2: A+B=0For x: −A+B+C=0For the constant term: A+C=1
Solve System of Equations: Solve the system of equations for A, B, and C. From A+B=0, we get B=−A. Substitute B=−A into −A+B+C=0 to get −A−A+C=0, which simplifies to −2A+C=0. Now we have two equations: A+C=1−2A+C=0
Find Values of A, B, C: Solve the system of equations.Subtract the second equation from the first to eliminate C:A+C−(−2A+C)=1−0A+C+2A−C=13A=1A=31
Write Partial Fraction Decomposition: Find B and C using the value of A.Since B=−A, B=−31.Substitute A into −2A+C=0 to find C:−2(31)+C=0−32+C=0C0
Integrate Each Term: Write the partial fraction decomposition with the found values of A, B, and C.x3+11=x+131+x2−x+1−31x+32
Integrate First Term: Integrate each term separately.∫31x+11dx+∫x2−x+1−31x+32dx
Complete the Square: The first integral is straightforward.∫31x+11dx=31ln∣x+1∣+C1
Rewrite Integral: The second integral requires completing the square for the quadratic denominator. x2−x+1 can be written as (x−21)2+43 by completing the square.
Split Integral: Rewrite the second integral with the completed square. ∫(x−21)2+(43)−31x+32dx
Integrate First Part: Split the second integral into two parts.\int\frac{-\frac{\(1\)}{\(3\)}x}{(x - \frac{\(1\)}{\(2\)})^\(2\) + \frac{\(3\)}{\(4\)}} dx + \int\frac{\frac{\(2\)}{\(3\)}}{(x - \frac{\(1\)}{\(2\)})^\(2\) + \frac{\(3\)}{\(4\)}} dx
Integrate Second Part: The first part of the second integral is a standard integral that results in an arctangent function after a substitution, and the second part is a logarithmic function.\(\newlineLet u=x−21, then du=dx, and the integral becomes:−31∫(u)2+(43)udu+32∫(u)2+(43)1du
Combine Integrals: Integrate the first part using the arctangent formula.−31∫u2+43udu=−31⋅32⋅arctan(32u)+C2
Combine Constants: Integrate the second part using the logarithmic formula.32∫(u)2+(43)1du=32×32×ln∣u+23∣−ln∣u−23∣+C3
Combine Constants: Integrate the second part using the logarithmic formula.32∫(u)2+(43)1du=32⋅32⋅ln∣u+23∣−ln∣u−23∣+CCombine the results of the integrals and substitute back for u.∫31x+11dx+∫x2−x+1−31x+32dx=31ln∣x+1∣−323arctan(32(x−21))+343ln∣(x−21)+23∣−ln∣(x−21)−23∣+C
Combine Constants: Integrate the second part using the logarithmic formula.32∫(u)2+(43)1du=32⋅32⋅ln∣u+23∣−ln∣u−23∣+C Combine the results of the integrals and substitute back for u.∫31x+11dx+∫x2−x+1−31x+32dx=31ln∣x+1∣−323arctan(32(x−21))+343ln∣(x−21)+23∣−ln∣(x−21)−23∣+C Combine the constants of integration into a single constant C.Final answer: ∫x3+11dx=31ln∣x+1∣−323arctan(32(x−21))+343ln∣(x−21)+23∣−ln∣(x−21)−23∣+C
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