Let f(x) = (2x² + x + 8) / ((2x−1)(x² + 2)).
- (i)Express f(x) in partial fractions.[5]
- (ii)Hence, showing full working, find ∫(from 1 to 5) f(x) dx, giving the answer in the form ln c, where c is an integer.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [B1] State or imply the form A/(2x-1) + (Bx+C)/(x²+2)
- [M1] Use a correct method for finding a constant
- [A1] Obtain one of A = 4, B = −1, C = 0
- [A1] Obtain a second value
- [A1] Obtain the third value
- [B1FT] Integrate and obtain term 2ln(2x−1)
- [*M1] Integrate and obtain term of the form kln(x²+2)
- [A1FT] Obtain term -(1/2)ln(x²+2)
- [DM1] Substitute limits correctly in an integral of the form aln(2x-1)+bln(x²+2), where ab ≠ 0
- [A1] Obtain answer ln 27 after full and correct exact working
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