1. Let f be a continuous function on the closed interval [0,1]. Which of the following statements about f must be true?

A. None

B. I only

C. II only

D. III only

E. The correct answer is not

given by A, B, C, or D.

 

Solution: The answer is C

 

Let f(x) = x/2. Then I and III are not true, for

 

 

 

Statement II is true.

Reason: Let r = x/2, then dx = 2dr. By substitution,

Note: The definite integral is a number that does not depend on x. Therefore, any letter can replace x.