Let us assume that

Also, let x = 0.49 so that x + Δx = 0.48

⇒ 0.49 + Δx = 0.48

∴ Δx = –0.01

On differentiating f(x) with respect to x, we get

We know

When x = 0.49, we have

Recall that if y = f(x) and Δx is a small increment in x, then the corresponding increment in y, Δy = f(x + Δx) – f(x), is approximately given as

Here, and Δx = –0.01

⇒ Δf = (0.7143)(–0.01)

∴ Δf = –0.007143

Now, we have f(0.48) = f(0.49) + Δf

⇒ f(0.48) = 0.7 – 0.007143

∴ f(0.48) = 0.692857

Thus,