Worked solution
Complete a square after substitution and use a product derivative
(a) By using the substitution , find . marks
(b) Find . mark
Hence find . marks
[2016/PJC/Promo/7]
CJC · Review Problems · Question 8
Answer
(a) ; (b) and .
(a)
Let , so . The integral becomes . Thus the answer is for .
How did this part go?
(b) Derivative
The product rule gives .
How did this part go?
(b) Hence integral
Use and , so and the preceding derivative gives . The integral is .
How did this part go?
Common mistakes
The log in the hence integral restricts x to positive inputs.