Nov 2022 p33 q11
2120
Let \(f(x) = \frac{5-x+6x^2}{(3-x)(1+3x^2)}\).
(a) Express \(f(x)\) in partial fractions.
(b) Find the exact value of \(\int_0^1 f(x) \, dx\), simplifying your answer.
Solution
(a) Express \(f(x)\) in the form \(\frac{A}{3-x} + \frac{Bx+C}{1+3x^2}\).
Equate coefficients to find \(A = 2\), \(B = 0\), and \(C = 1\).
(b) Integrate to obtain \(-2 \ln(3-x)\) and \(\frac{1}{\sqrt{3}} \arctan(\sqrt{3}x)\).
Substitute limits to find \(2 \ln \frac{3}{2} + \frac{1}{\sqrt{3}} \pi\).
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