The diagram shows the curves y = e^2x and y = 8e^-x. The shaded region is bounded by the two curves and the y-axis. [Figure]
- (a)Show that the x-coordinate of the point of intersection of the two curves is ln2.[2]
- (b)Find the area of the shaded region.[3]
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Mark scheme
Marking points from the official mark scheme (Feb/Mar 2025). The mark or mark type is shown in brackets.
- [B1] State e^2x = 8e^-x and obtain 3x=ln8 or e^x = 2 or equivalent
- [B1] Confirm x = ln 2 AG Necessary detail needed.
- [B1] Substitute x=ln2 in either e^2x or 8e^-x and obtain value 4
- [B1] Substitute in other expression, obtain value 4 and conclude appropriately AG Necessary detail needed.
- [B1] Integrate 8e^-x - e^2x to obtain –8e^-x – ½e^2x OE, involving separate integrations.
- [M1] Apply limits correctly and simplify to eliminate e and ln
- [A1] Obtain –8×½ – ½×4 + 8 + ½ or equivalent, and hence ½ or equivalent
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