Here are the solutions for the integrals using partial fractions:
3.1
∫(3x+2)2(x2−1)x3+5x2−3x−1dx
Step 1: Factor the denominator completely and set up the partial fraction decomposition.
The denominator is (3x+2)2(x2−1)=(3x+2)2(x−1)(x+1).
The partial fraction decomposition is:
(3x+2)2(x−1)(x+1)x3+5x2−3x−1=3x+2A+(3x+2)2B+x−1C+x+1D
Multiply both sides by the common denominator (3x+2)2(x−1)(x+1):
x3+5x2−3x−1=A(3x+2)(x−1)(x+1)+B(x−1)(x+1)+C(3x+2)2(x+1)+D(3x+2)2(x−1)
Step 2: Solve for the coefficients A, B, C, and D.
• Set x=1:
13+5(1)2−3(1)−1=C(3(1)+2)2(1+1)
2=C(5)2(2)⟹2=50C⟹C=502=251
• Set x=−1:
(−1)3+5(−1)2−3(−1)−1=D(3(−1)+2)2(−1−1)
−1+5+3−1=D(−1)2(−2)⟹6=−2D⟹D=−3
• Set x=−32:
(−32)3+5(−32)2−3(−32)−1=B(−32−1)(−32+1)
−278+920+2−1=B(−35)(31)
27−8+60+27=−95B⟹2779=−95B⟹B=2779⋅(−59)=−1579
• Compare coefficients of x3:
The expanded equation is x3+5x2−3x−1=A(3x3+2x2−3x−2)+B(x2−1)+C(9x3+21x2+16x+4)+D(9x3+3x2−8x−4).
Comparing coefficients of x3:
1=3A+9C+9D
1=3A+9(251)+9(−3)
1=3A+259−27⟹1=3A+259−675⟹1=3A−25666
3A=1+25666=2525+666=25691⟹A=75691
Step 3: Integrate each term of the partial fraction decomposition.
∫(3x+2691/75+(3x+2)2−79/15+x−11/25+x+1−3)dx
=75691∫3x+21dx−1579∫(3x+2)−2dx+251∫x−11dx−3∫x+11dx
=75691(31ln∣3x+2∣)−1579(31−1(3x+2)−1)+251ln∣x−1∣−3ln∣x+1∣+K
Step 4: Simplify and combine the results.
\frac{691{225}\ln|3x+2| + \frac{79}{45(3x+2)} + \frac{1}{25}\ln|x-1| - 3\ln|x+1| + K}
3.2
∫(3−2x)38x3−x2+4x−3dx
Step 1: Use a substitution to simplify the denominator.
Let u=3−2x. Then 2x=3−u, so x=23−u.
Also, du=−2dx, which means dx=−21du.
Step 2: Substitute x and dx into the integral and simplify the numerator.
Numerator: 8x3−x2+4x−3
=8(23−u)3−(23−u)2+4(23−u)−3
=88(3−u)3−4(3−u)2+2(3−u)−3
=(27−27u+9u2−u3)−41(9−6u+u2)+(6−2u)−3
=−u3+(9−41)u2+(−27+23−2)u+(27−49+6−3)
=−u3+435u2−255u+4111
The integral becomes:
∫u3−u3+435u2−255u+4111(−21)du
=−21∫(u3−u3+4u335u2−2u355u+4u3111)du
=−21∫(−1+4u35−2u255+4u3111)du
Step 3: Integrate each term with respect to u.
=−21(−u+435ln∣u∣−255(−u1)+4111(−2u21))+C
=−21(−u+435ln∣u∣+2u55−8u2111)+C
=21u−835ln∣u∣−4u55+16u2111+C
Step 4: Substitute back u=3−2x.
\frac{1{2}(3-2x) - \frac{35}{8}\ln|3-2x| - \frac{55}{4(3-2x)} + \frac{111}{16(3-2x)^2} + C}
The constant term 23 from 21(3−2x) can be absorbed into the integration constant C.
So, an equivalent form is:
-x - \frac{35{8}\ln|3-2x| - \frac{55}{4(3-2x)} + \frac{111}{16(3-2x)^2} + C}
3 done, 2 left today. You're making progress.