Answer only one of the following alternatives. OR The diagram shows part of the curve y = 8 + e⁻ˣ/³ crossing the y-axis at P. The normal to the curve at P meets the x-axis at Q. (i) Find the coordinates of Q. (ii) The line through Q, parallel to the y-axis, meets the curve at R and OQRS is a rectangle. Find ∫[0 to -3] (8 + e⁻ˣ/³) dx and hence find the area of the shaded region.
- (i)Find the coordinates of Q.[4]
- (ii)Find ∫[0 to -3] (8 + e⁻ˣ/³) dx and hence find the area of the shaded region.[6]
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Mark scheme
Marking points from the official mark scheme (Oct/Nov 2012). The mark or mark type is shown in brackets.
- [M1] dy/dx = (-1/3)e⁻ˣ/³
- [A1] at (0, 9) dy/dx = -1/3
- [M1] Grad normal = 3
- [A1] Point Q is (-3, 0)
- [M1] Area rectangle 24 + 3e (32.1)
- [M1] Integrate: 8x and e⁻ˣ/³ seen
- [A1] [8x - 3e⁻ˣ/³]
- [M1] Correct use of limits their -3 and 0
- [A1] 21+3e (29.1)
- [A1] Shaded area =3
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