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BAC2 ss · Mathematics
derivatives · Derivatives

Differentiation rules

Calculating a derivative from the definition, with the limit, is slow and only serves to understand where it comes from. To work with real functions —costs, revenues, populations— you need rules that turn that derivative into a mechanical calculation. This section brings together the rules for combining functions and the table of common functions that you will use in every problem in the unit.

Before you start, make sure you know: Definition of the derivative of a function at a point (1st Bachillerato)
Before you start, make sure you know: Logarithms (1st Bachillerato)

Basic rules: power, sum and constant

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Calculate the derivative of the following polynomial functions using the basic rules of differentiation: a) $f(x) = 5x^3 - 2x^2 + 7x - 10$ b)…

Calculate the derivative of the following polynomial functions using the basic rules of differentiation:

  1. a) $f(x) = 5x^3 - 2x^2 + 7x - 10$
  1. b) $g(x) = \frac{1}{4}x^4 + \frac{2}{3}x^3 - 5$
  1. c) $h(x) = x^5 - \sqrt{2}x$
Solve
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A content creator has observed that the number of views of one of their videos on a social network follows the function $f(t) = t^2 + 20t + 100$, where $t$ is the time…

A content creator has observed that the number of views of one of their videos on a social network follows the function $f(t) = t^2 + 20t + 100$, where $t$ is the time in hours since it was published.

Calculate the Average Rate of Change (A.R.O.C.) of the number of views in the interval $[1, 4]$. Interpret the result obtained in the context of the problem.

1 2 3 4 5 t (h) 125 150 175 200 225 f(t) f(1) f(4) Δt = 3 Δf = ? A.R.O.C. = ? f(t) = t² + 20t + 100
Solve

The product rule

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Given the function $f(x) = (3x - 5) \cdot e^x$, find its derivative by applying the product rule. Simplify the result by factorising where possible.

Given the function $f(x) = (3x - 5) \cdot e^x$, find its derivative by applying the product rule. Simplify the result by factorising where possible.

Solve
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A cosmetics company has estimated that the daily profit (in hundreds of euros) generated by the sale of a new facial serum follows the function…

A cosmetics company has estimated that the daily profit (in hundreds of euros) generated by the sale of a new facial serum follows the function $B(t) = 20t \cdot e^{-0,2t}$, where $t$ is the time in months since its launch. The figure shows the graph of $B(t)$ and marks the point corresponding to $t=5$.

  1. a) Obtain the expression of the function $B'(t)$, which represents the rate of change of the profit.
  1. b) Calculate the value of the derivative 5 months after its launch and interpret the result obtained in economic terms.
Graph of the function B(t) = 20t·e^(-0,2t) for t between 0 and 16 months, with the point with abscissa t = 5 marked5101510203040t (months)B (hundreds of €)B(t)
Solve

The quotient rule

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Calculate the derivative of the following rational function using the quotient rule: $$f(x) = \frac{2x + 3}{x - 1}$$ State for which values of $x$ the derivative of this…

Calculate the derivative of the following rational function using the quotient rule:

$$f(x) = \frac{2x + 3}{x - 1}$$

State for which values of $x$ the derivative of this function does not exist, based on its domain.

Solve
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Consider the function $f(x) = \dfrac{e^{2x}}{x^2 + 1}$. a) Calculate its derivative $f'(x)$, simplifying the expression as much as possible. b) Determine whether there…

Consider the function $f(x) = \dfrac{e^{2x}}{x^2 + 1}$.

  1. a) Calculate its derivative $f'(x)$, simplifying the expression as much as possible.
  1. b) Determine whether there is any point where the curve has a horizontal tangent (zero gradient). If so, state the coordinates of that point.
Solve
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Given the function $f(x) = \dfrac{x^2 + k}{x - 1}$, calculate the value of the constant $k$ knowing that the gradient of the tangent line to the graph of $f(x)$ at the…

Given the function $f(x) = \dfrac{x^2 + k}{x - 1}$, calculate the value of the constant $k$ knowing that the gradient of the tangent line to the graph of $f(x)$ at the point with abscissa $x = 2$ is equal to $-3$. Once $k$ has been found, write the complete equation of this tangent line.

Solve

Table of common derivatives (with the chain rule)

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Apply the chain rule to find the derivative of the following composite functions: a) $f(x) = (2x^2 + 1)^4$ b) $g(x) = \ln(5x - 2)$ c) $h(x) = e^{3x^2}$

Apply the chain rule to find the derivative of the following composite functions:

  1. a) $f(x) = (2x^2 + 1)^4$
  1. b) $g(x) = \ln(5x - 2)$
  1. c) $h(x) = e^{3x^2}$
Solve
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Given the function $f(x) = \sqrt{x^2 + 9}$, calculate its derivative using the chain rule. Once obtained, find the value of the gradient of the tangent line to the curve…

Given the function $f(x) = \sqrt{x^2 + 9}$, calculate its derivative using the chain rule. Once obtained, find the value of the gradient of the tangent line to the curve at the point $x = 4$.

x y x=4 f(4) f(x) = √(x² + 9) Tangent line dx dy m = f'(4)
Solve
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Consider the curve $y = x^3 - 6x^2 + 4$ and the line $r: y = -9x + 2$. a) Find the points of the curve at which the tangent line is parallel to the line $r$. b) Write…

Consider the curve $y = x^3 - 6x^2 + 4$ and the line $r: y = -9x + 2$.

  1. a) Find the points of the curve at which the tangent line is parallel to the line $r$.
  1. b) Write the equations of the tangent lines to the curve at those points.
Solve

Combinations and logarithmic differentiation

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Given the function $f(x) = x^2 \cdot \ln(x)$, calculate: a) The first derivative $f'(x)$. b) The second derivative $f''(x)$. c) The equation of the normal line to the…

Given the function $f(x) = x^2 \cdot \ln(x)$, calculate:

  1. a) The first derivative $f'(x)$.
  1. b) The second derivative $f''(x)$.
  1. c) The equation of the normal line to the graph at the point with abscissa $x = e$. (Remember that the normal line is perpendicular to the tangent at the point of contact).
1 2 3 4 5 2 4 6 8 0 x y e e² f(x) = x²·ln(x) Tangent Normal
Solve
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Apply the technique of logarithmic differentiation to find the expression for the derivative of: $f(x) = (x^2 + 1)^{\ln(x)}$

Apply the technique of logarithmic differentiation to find the expression for the derivative of:

$f(x) = (x^2 + 1)^{\ln(x)}$

Solve
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Calculate the derivative function of the following expression using logarithmic differentiation. Take into account that the base and the exponent are functions of $x$:…

Calculate the derivative function of the following expression using logarithmic differentiation. Take into account that the base and the exponent are functions of $x$:

$$f(x) = (3x^2 + 1)^{\text{sen}(x)}$$

Show all intermediate steps, applying the laws of logarithms correctly before differentiating.

Solve
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Given the rational function $f(x) = \frac{1}{2x - 3}$, obtain a general expression for its nth derivative, $f^{(n)}(x)$. To do this, calculate the 1st, 2nd, 3rd, and 4th…

Given the rational function $f(x) = \frac{1}{2x - 3}$, obtain a general expression for its nth derivative, $f^{(n)}(x)$.

To do this, calculate the 1st, 2nd, 3rd, and 4th order derivatives, identify the pattern in numbers and signs, and write it in terms of $n$ and the factorial $n!$.

Solve

Summary

See all the exercises in this section