Four economists, Amara, Biruk, Chen, and Dalia, are attempting to determine the indefinite integral representing a total utility function:
∫1v dv\int \frac{1}{v} \, dv∫v1dv
for v>0v > 0v>0. Each economist proposes a different general form for the result:
Amara: ∫1v dv=lnv\int \frac{1}{v} \, dv = \ln v∫v1dv=lnv
Biruk: ∫1v dv=Alnv\int \frac{1}{v} \, dv = A \ln v∫v1dv=Alnv
Chen: ∫1v dv=ln(kv)\int \frac{1}{v} \, dv = \ln(kv)∫v1dv=ln(kv)
Dalia: ∫1v dv=lnv+C\int \frac{1}{v} \, dv = \ln v + C∫v1dv=lnv+C
(i) Explain why Amara's result is incomplete.
(ii) Explain why Biruk's answer is incorrect as a general anti-derivative of 1v\frac{1}{v}v1.
Using the properties of logarithms, demonstrate why Chen and Dalia's forms can be considered equivalent for certain values of the constants kkk and CCC.
Practise Edexcel A Level Maths 11.1 Integrating Standard Functions with exam-style questions for A Level Maths. 81 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.