Let f(x) = (5x² - 7x + 4) / ((3x + 2)(x² + 5)).
- (i)Express f(x) in partial fractions.[5]
- (ii)Hence obtain the expansion of f(x) in ascending powers of x, up to and including the term in x².[5]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [B1] State or imply the form A/(3x+2) + (Bx+C)/(x²+5)
- [M1] Use a relevant method to determine a constant
- [A1] Obtain one of the values A = 2, B = 1, C = -3
- [A1] Obtain a second value
- [A1] Obtain the third value
- [M1] Use correct method to find the first two terms of the expansion of (3x + 2)⁻¹, (1 + (3/2)x)⁻¹, (5+x²)⁻¹ or (1+(1/5)x²)⁻¹
- [A1FT] Obtain correct unsimplified expansions up to the term in x² of each partial fraction. The FT is on A, B, C. from part (i)
- [A1FT] (Second A1FT for the other fraction)
- [M1] Multiply out up to the term in x² by Bx + C, where BC ≠ 0
- [A1] Obtain final answer 2 - (13/10)x + (237/100)x² , or equivalent
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