# Lecture 10 Application of Derivatives

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# Lecture - 10 Chapter 6 Application of Derivatives

In this lecture, I am discussing method to find approximate values of roots using derivatives and questions from NCERT Exercise 6.4

Questions discussed in this lecture:

 NCERT EXERCISE 6.4 (Approximations)

Question 2. Find the approximate value of f(2.01), where $f(x) = 4x^2 + 5x +2$.

Question 3. Find the approximate value of f(5.001), where $f(x) = x^3 – 7x^2 +15$.

Question 4. Find the approximate change in the volume V of a cube of side x metres caused by increasing the side by 1%.

Question 5. Find the approximate change in the surface area of a cube of side x metres caused by decreasing the side by 1%.

Question 6. If the radius of a sphere is measured as 7 m with an error of 0.02 m, then find the approximate error in calculating its volume.

Question 7. If the radius of a sphere is measured as 9 m with an error of 0.03 m, then find the approximate error in calculating its surface area.

Question 8. If $f(x) = 3x^2 + 15x + 5$, then the approximate value of f (3.02) is
(A) 47.66
(B) 57.66
(C) 67.66
(D) 77.66

Question 9. The approximate change in the volume of a cube of side x metres caused by increasing the side by 3% is
(A)  $0.06 x^3 m^3$
(B)  $0.6 x^3 m^3$
(C)  $0.09 x^3 m^3$
(D)  $0.9 x^3 m^3$