Let π(π₯) be a continuous function from β to β such that π(π₯) = 1 β π(2 ββ¦
2024
Let π(π₯) be a continuous function from β to β such that
Β Β Β Β Β Β Β Β Β Β Β Β Β Β Β Β π(π₯) = 1 β π(2 β π₯)
Which one of the following options is the CORRECT value of \(β«_0^2 π(π₯)ππ₯\)?
- A.
0
- B.
1
- C.
2
- D.
β1
Attempted by 45 students.
Show answer & explanation
Correct answer: B
Key property: f(x) + f(2 β x) = 1 for all real x.
Let I = β«_0^2 f(x) dx.
Integrate the given relation over [0,2]: β«_0^2 f(x) dx + β«_0^2 f(2 β x) dx = β«_0^2 1 dx = 2.
Change variables in the second integral with u = 2 β x. Then β«_0^2 f(2 β x) dx = β«_2^0 f(u) (βdu) = β«_0^2 f(u) du = I.
Therefore I + I = 2, so 2I = 2 and I = 1.
Conclusion: β«_0^2 f(x) dx = 1.
A video solution is available for this question β log in and enroll to watch it.