A function f:R→R defined by f(x) = 3 - 4x is-

We have f: R→R defined by f(x) = 3 - 4x

Let x₁, x₂ ∈R such that f(x₁) = f(x₂)

⇒3 - 4x₁ = 3 -4 x₂

⇒ - 4x₁ =  -4 x₂

⇒ x₁ =  x₂

so f is one-one.

For any real number (y) in R, there exist {(3- y)/4} in R such that

f{(3-y)/4} = 3 - 4{(3- y)/4} = y

so f is onto.

Hence f is one-one onto.