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Date May 2008 Marks available 5 Reference code 08M.2.hl.TZ2.3
Level HL only Paper 2 Time zone TZ2
Command term Find Question number 3 Adapted from N/A

Question

The curve \(y = {{\text{e}}^{ - x}} - x + 1\) intersects the x-axis at P.

(a)     Find the x-coordinate of P.

(b)     Find the area of the region completely enclosed by the curve and the coordinate axes.

Markscheme

(a)     Either solving \({{\text{e}}^{ - x}} - x + 1 = 0\) for x, stating \({{\text{e}}^{ - x}} - x + 1 = 0\), stating P(x, 0) or using an appropriate sketch graph.     M1

x = 1.28     A1     N1

Note: Accept P(1.28, 0) .

 

(b)     Area \( = \int_0^{1.278...} {({{\text{e}}^{ - x}} - x + 1){\text{d}}x} \)     M1A1

= 1.18     A1     N1

Note: Award M1A0A1 if the dx is absent.

 

[5 marks]

Examiners report

This was generally well done. In part (a), most candidates were able to find x = 1.28 successfully. A significant number of candidates were awarded an accuracy penalty for expressing answers to an incorrect number of significant figures.

Part (b) was generally well done. A number of candidates unfortunately omitted the dx in the integral while some candidates omitted to write down the definite integral and instead offered detailed instructions on how they obtained the answer using their GDC.

Syllabus sections

Topic 6 - Core: Calculus » 6.5 » Area of the region enclosed by a curve and the \(x\)-axis or \(y\)-axis in a given interval; areas of regions enclosed by curves.
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