Challenging +1.8 This is a Further Maths question requiring partial fractions decomposition (with both quadratic and linear factors), integration of rational functions including arctangent, and proper treatment of an improper integral with limits to infinity. While the techniques are standard for Further Maths, the combination of skills, careful algebraic manipulation, and rigorous limiting process across 8 marks makes this substantially harder than average A-level questions, though not exceptionally difficult for Further Maths students who have practiced these methods.
Evaluate the improper integral \(\int_0^{\infty} \frac{4x - 30}{(x^2 + 5)(3x + 2)} \, dx\), showing the limiting process used.
Give your answer as a single term.
[8 marks]
Question 10:
10 | Splits integrand into partial
fractions of the form
Ax B C
x2 5 3x2 | AO3.1a | M1 | 4x 30 AxB C
(x2 5)(3x 2) x2 5 3x2
4x30(AxB)3x2C x25
Compare coefficients of x:
42A+3B
Compare coeffcients of x2:
03AC
Compare constant terms
302B+5C
302B15A
43B
302B15( )
2
B0
A2
C6
4x30 2x 6
dx dx
(x2 5)(3x2) x25 3x2
ln(x25)2ln(3x2)c
4x 30
dx
0 (x2 5)(3x 2)
a 2x 6
lim dx
0 x25 3x2
a
a
limln(x2 5)2ln(3x2)
0
a
a
x25
limln
(3x2)2
a
0
a25 5
limln ln
a 9a212x4 4
1 5
ln ln
9 4
4
ln
45
Sets up an identity from which to
solve for A, B and C | AO1.1a | M1
Obtains correct values of
A, B and C
CAO | AO1.1b | A1
Integrates ‘their’ two terms
correctly
FT provided both M1 marks
awarded | AO1.1b | A1F
Applies the laws of logs to ‘their’
integral correctly | AO1.1a | M1
Applies limits (a and 0) to ‘their’
integral correctly | AO1.1a | M1
Shows the limiting process used
with clear detailed working | AO2.1 | R1
Obtains correct single term solution
CAO | AO1.1b | A1
Total | 8
Q | Marking Instructions | AO | Marks | Typical Solution
Evaluate the improper integral $\int_0^{\infty} \frac{4x - 30}{(x^2 + 5)(3x + 2)} \, dx$, showing the limiting process used.
Give your answer as a single term.
[8 marks]
\hfill \mbox{\textit{AQA Further Paper 2 Q10 [8]}}