Question:
Let A = R – {3}, B = R – {1}. Let f : A → B be defined by f (x) = x – 2/ x – 3 ∀ x ∈ A . Then show that f is bijective.
Solution:
Given,
A = R – {3}, B = R – {1}
And,
f : A → B be defined by f (x) = x – 2/ x – 3 ∀ x ∈ A
Hence, f (x) = (x – 3 + 1)/ (x – 3) = 1 + 1/ (x – 3)
Let f(x1) = f (x2)
$1+\frac{1}{x_{1}-3}=1+\frac{1}{x_{2}-3}$
$\frac{1}{x_{1}-3}=\frac{1}{x_{2}-3}$
$x_{1}=x_{2}$
So, f (x) is an injective function.
Now let y = (x – 2)/ (x -3)
x – 2 = xy – 3y
x(1 – y) = 2 – 3y
x = (3y – 2)/ (y – 1)
y ∈ R – {1} = B
Thus, f (x) is onto or subjective.
Therefore, f(x) is a bijective function.