solution:
Think about f : R → R given by f(x) = 4x + 3
Say, x, y ∈ R
Let f(x) = f(y) then, at that point 4x + 3 = 4y + 3
x = y
f is one-one capacity.
Let y ∈ Range of f y = 4x + 3
or on the other hand x = (y-3)/4
Here, f((y-3)/4) = 4( (y-3)/4) + 3 = y This suggests f(x) = y
So f is onto
Subsequently, f is invertible.
Opposite of f is x = f – 1 (y) = (y-3)/4.