resolve into partial fraction. x+5÷(2x-1) (x+4)
Answers
Answer:
Answer
Let
(x+3)(x+1)
2
(2x−5)
=
x+3
A
+
x+1
B
+
(x+1)
2
C
⇒2x−5=A(x+1)
2
+B(x+1)(x+3)+C(x+3)
⇒2x−5=A(x
2
+2x+1)+B(x
2
+4x+3)+C(x+3)
On comparing coefficients
0=A+B,2=2A+4B+C,−5=A+3B+3C
⇒A=−
4
11
,B=
4
11
,C=−
2
7
Hence,
(x+3)(x+1)
2
(2x−5)
=−
4(x+3)
11
+
4(x+1)
11
−
2(x+1)
2
7
Hence, option 'B' is correct.
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EXPLANATION.
⇒ ∫x + 5/(2x - 1)(x + 4).dx.
As we know that,
Partial fraction is apply only when coefficient of Denominator > coefficient of Numerator.
⇒ ∫x + 5/(2x - 1)(x + 4).dx = A/(2x - 1) + B/(x + 4).
Taking L.C.M on both sides, we get.
⇒ x + 5/(2x - 1)(x + 4) = A/(2x - 1) + B/(x + 4).
⇒ x + 5 = A(x + 4) + B(2x - 1).
Put the value of x = -4 in equation, we get.
⇒ - 4 + 5 = A(- 4 + 4) + B[2(-4) - 1].
⇒ 1 = 0 + B[- 8 - 1].
⇒ 1 = - 9B.
⇒ B = -1/9.
Put the value of x = 1/2 in equation, we get.
⇒ 1/2 + 5 = A(1/2 + 4) + B[2(1/2) - 1].
⇒ 1 + 10/2 = A(1 + 8/2) + 0.
⇒ 11/2 = 9A/2.
⇒ 11 = 9A.
⇒ A = 11/9.
Put the value of A & B in equation, we get.
⇒ ∫x + 5/(2x - 1)(x + 4).dx = ∫A/(2x - 1).dx + ∫B/(x + 4).dx.
⇒ ∫x + 5/(2x - 1)(x + 4).dx = ∫11/9/(2x - 1).dx + ∫-1/9/(x + 4).dx.
⇒ ∫11/9(2x - 1).dx + ∫-1/9(x + 4).dx.
⇒ 11/9㏑(2x - 1) + (-1)/9㏑(x + 4) + c.
⇒ 11/9㏑(2x - 1) - 1/9㏑(x + 4) + c.
MORE INFORMATION.
Standard integral.
(1) = ∫0.dx = c.
(2) = ∫1.dx = x + c.
(3) = ∫k dx = kx + c, (k ∈ R).
(4) = ∫xⁿdx = xⁿ⁺¹/n + 1 + c, (n ≠ -1).
(5) = ∫dx/x = ㏒(x) + c.
(6) = ∫eˣdx = eˣ + c.
(7) = ∫aˣdx = aˣ/㏒ₐ(e) + c. = ㏒ₐ(e) + c.