Question:

Find the approximate value of f (2.01), where f (x) = 4x2+5x + 2

Updated On: Sep 15, 2023
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Solution and Explanation

Let x = 2 and ∆x = 0.01. Then, we have: f(2.01) = f(x + ∆x) = 4(x + ∆x)2 + 5(x + ∆x) + 2 Now, ∆y = f(x + ∆x) − f(x)

∴ f(x + ∆x) = f(x) + ∆y

f(2.01)≈(4x2+5x+2)+(8x+5)∆x

28+0.21

=28.21

Hence, the approximate value of f (2.01) is 28.21.

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Concepts Used:

Application of Derivatives

Various Applications of Derivatives-

Rate of Change of Quantities:

If some other quantity ‘y’ causes some change in a quantity of surely ‘x’, in view of the fact that an equation of the form y = f(x) gets consistently pleased, i.e, ‘y’ is a function of ‘x’ then the rate of change of ‘y’ related to ‘x’ is to be given by 

\(\frac{\triangle y}{\triangle x}=\frac{y_2-y_1}{x_2-x_1}\)

This is also known to be as the Average Rate of Change.

Increasing and Decreasing Function:

Consider y = f(x) be a differentiable function (whose derivative exists at all points in the domain) in an interval x = (a,b).

  • If for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≤ f(x2); then the function f(x) is known as increasing in this interval.
  • Likewise, if for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≥ f(x2); then the function f(x) is known as decreasing in this interval.
  • The functions are commonly known as strictly increasing or decreasing functions, given the inequalities are strict: f(x1) < f(x2) for strictly increasing and f(x1) > f(x2) for strictly decreasing.

Read More: Application of Derivatives