The curve C has equation y = 2x² for 0 ≤ x ≤ 4. Find
- (i)the mean value of y with respect to x for 0 ≤ x ≤ 4,[3]
- (ii)the y-coordinate of the centroid of the region enclosed by C, the line x = 4 and the x-axis.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2012). The mark or mark type is shown in brackets.
- [M1] Uses formula for mean value: (1/4) ∫ (from 0 to 4) 2x² dx
- [M1A1] Integrates: (1/4) [2x³/3] (from 0 to 4) = 32/3
- [M1] Uses formula for y-coordinate: (1/2) ∫ (from 0 to 4) y² dx / ∫ (from 0 to 4) y dx
- [M1A1] Integrates: (1/2) [4x⁵/5] (from 0 to 4) / [2x³/3] (from 0 to 4) = 48/5
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