Let f(x) = 2 / ((2x−1)²(2x + 1)).
- (a)Express f(x) in partial fractions.[2]
- (b)Using your answer to part (a), show that (f(x))² = 1/((2x−1)²) - 1/(2x−1) + 1/(2x+1) + 1/((2x + 1)²).[2]
- (c)Hence show that ∫₁² (f(x))² dx = ⁸/₁₅ + ½ ln(⁵/₃).[5]
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [M1] State or imply the form A/(2x-1) + B/(2x+1) and use a relevant method to find A or B
- [A1] Obtain A = 1, B = -1
- [M1] Square the result of part (a) and substitute the fractions of part (a)
- [A1] Obtain the given answer correctly
- [B3, 2, 1, 0] Integrate and obtain -1/(2(2x-1)) - ½ln(2x-1) + ½ln(2x+1) - 1/(2(2x+1)), or equivalent
- [M1] Substitute limits correctly
- [A1] Obtain the given answer correctly
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