The diagram below shows part of the curve y = 3x - 14 + 32/x² cutting the x-axis at the points P and Q. [Figure 12.1]
- (i)Show that x - 2 is a factor of 3x³ - 14x² + 32.[1]
- (ii)Hence factorise 3x³ - 14x² + 32 completely.[4]
- (iii)State the x-coordinates of P and Q.[1]
- (iv)Find ∫ (3x - 14 + 32/x²) dx and hence determine the area of the shaded region.[4]
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Mark scheme
Marking points from the official mark scheme (Oct/Nov 2014). The mark or mark type is shown in brackets.
- [B1] (i) f(2)= 3(2³)-14(2²)+ 32 = 0. Or complete long division
- [M1] (ii) (x-2)(3x²-8x-16). 3x² and 16
- [A1] (ii) 8x and correct signs
- [M1] (ii) (x-2)(x-4)(3x+4). Factorise three term quadratic
- [A1] (ii)
- [B1] (iii) x = 2, 4
- [B1] (iv) ∫ (3x-14+32/x²) dx = 1.5x²-14x-32/x (+c). first 2 terms
- [B1] (iv) third term correct unsimplified
- [M1] (iv) Area = [1.5x²-14x-32/x] evaluated from 2 to 4. Limits of 2 and 4 and subtract
- [A1] (iv) = (-) 2
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