Question

Let f(x)=dfracax+bcx+d, then f∘ f(x)=x, provided that:

• A. \(d=-a\)
• B. \(d=a\)
• C. \(a=b=1\)
• D. a=b=c=d=1

Hint:

A function satisfying f(f(x))=x is called an involution.

Answer 1

The Correct Option is B