Q.

Suppose f(x)=(x+1)2 for x≥-1. If g(x) is the function whose graph is the reflection of the graph of f(x) with respect to the line y=x, then g(x) equals      [2002]

1 -x-1, x≥0  
2 1(x+1)2, x>-1  
3 x+1, x≥-1  
4 x-1, x≥0  

Ans.

(4)

Given:  f(x)=(x+1)2,    x≥-1

If g(x) is the reflection of f(x) in the line y=x, then it can be obtained by interchanging x and y in f(x)

i.e., y=(x+1)2  changes to x=(y+1)2

⇒  y+1=x   [y+1≠-x, since y≥-1]

⇒  y=x-1,   defined ∀x≥0

∴  g(x)=x-1,  ∀ x≥0