Let f(x) = x² + x + 6 x²(x + 2) (i) Express f(x) in partial fractions. (ii) Hence, showing full working, show that the exact value of S 4 f(x) dx is 2. [5]
- (i)Express f(x) in partial fractions.[5]
- (ii)Hence, showing full working, show that the exact value of S 4 f(x) dx is 2.[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/x + B/x² + C/(x+2)
- [M1] Use a correct method for finding a constant
- [A1] Obtain one of A = − 1, B = 3, C = 2
- [A1] Obtain a second value
- [A1] Obtain the third value
- [B1] Integrate and obtain terms ln|x| - 3/x + 2ln|x+2|
- [M1] Substitute limits correctly in an integral with terms a ln x, b/x and c ln(x+2), where abc ≠ 0
- [A1] Obtain (9/4) following full and exact working AG
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