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Last updated on October 8, 2025

Derivative of 3x³

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We use the derivative of 3x³, which is 9x², as a tool for understanding how the cubic function changes in response to a slight change in x. Derivatives help us calculate profit or loss in real-life situations. We will now talk about the derivative of 3x³ in detail.

Derivative of 3x³ for US Students
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What is the Derivative of 3x³?

We now understand the derivative of 3x³. It is commonly represented as d/dx (3x³) or (3x³)', and its value is 9x². The function 3x³ has a clearly defined derivative, indicating it is differentiable for all real numbers.

 

The key concepts are mentioned below:

 

Power Rule: A rule for differentiating functions of the form xⁿ.

 

Constant Multiple Rule: A rule for differentiating a constant times a function.

 

Polynomial Function: A function consisting of terms that are non-negative integer powers of x.

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Derivative of 3x³ Formula

The derivative of 3x³ can be denoted as d/dx (3x³) or (3x³)'.

 

The formula we use to differentiate 3x³ is: d/dx (3x³) = 9x²

 

The formula applies to all real numbers x.

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Proofs of the Derivative of 3x³

We can derive the derivative of 3x³ using proofs. To show this, we will use the basic rules of differentiation.

 

There are several methods we use to prove this, such as:

 

  • By First Principle
     
  • Using Power Rule

 

We will now demonstrate that the differentiation of 3x³ results in 9x² using the above-mentioned methods:

 

By First Principle

 

The derivative of 3x³ can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient. To find the derivative of 3x³ using the first principle, we will consider f(x) = 3x³. Its derivative can be expressed as the following limit: f'(x) = limₕ→₀ [f(x + h) - f(x)] / h … (1) Given that f(x) = 3x³, we write f(x + h) = 3(x + h)³. Substituting these into equation (1), f'(x) = limₕ→₀ [3(x + h)³ - 3x³] / h = limₕ→₀ [3(x³ + 3x²h + 3xh² + h³) - 3x³] / h = limₕ→₀ [9x²h + 9xh² + 3h³] / h = limₕ→₀ [9x² + 9xh + 3h²] = 9x² (as h approaches 0, the terms with h vanish) Hence, proved.

 

Using Power Rule

 

To prove the differentiation of 3x³ using the power rule, We use the formula: d/dx (xⁿ) = nxⁿ⁻¹ For 3x³, we consider the constant multiple rule: d/dx (3x³) = 3 * d/dx (x³) = 3 * 3x² = 9x² Thus, the derivative is 9x².

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Higher-Order Derivatives of 3x³

When a function is differentiated several times, the derivatives obtained are referred to as higher-order derivatives. Higher-order derivatives can be a little tricky. To understand them better, think of a car where the speed changes (first derivative) and the rate at which the speed changes (second derivative) also changes. Higher-order derivatives make it easier to understand functions like 3x³.

 

For the first derivative of a function, we write f′(x), which indicates how the function changes or its slope at a certain point. The second derivative is derived from the first derivative, which is denoted using f′′(x). Similarly, the third derivative, f′′′(x) is the result of the second derivative and this pattern continues.

 

For the nth derivative of 3x³, we generally use fⁿ(x) for the nth derivative of a function f(x), which tells us the change in the rate of change (continuing for higher-order derivatives).

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Special Cases:

When x is 0, the derivative of 3x³ = 9x², which is 0. There are no undefined points in the domain of 3x³, as it is differentiable for all real numbers.

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Common Mistakes and How to Avoid Them in Derivatives of 3x³

Students frequently make mistakes when differentiating 3x³. These mistakes can be resolved by understanding the proper solutions. Here are a few common mistakes and ways to solve them:

Mistake 1

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Not applying the power rule correctly

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Students may forget to apply the power rule correctly, leading to incorrect results. They often skip steps and directly arrive at the result.

 

Ensure that each step is written in order. Students might think it is awkward, but it is important to avoid errors in the process.

Mistake 2

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Ignoring constant multipliers

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They might not account for the constant multiplier in 3x³. Remember to multiply the constant outside the derivative of x³.

 

It will help you understand that the function's slope is scaled by the constant.

Mistake 3

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Confusion with higher-order derivatives

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While calculating higher-order derivatives, students might forget to apply the differentiation rules multiple times. For example, incorrect calculation for the second derivative: d²/dx² (3x³) might be mistakenly calculated as 3.

 

The correct method: d²/dx² (3x³) = d/dx (9x²) = 18x. To avoid this mistake, write each differentiation step clearly.

Mistake 4

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Not simplifying expressions

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There is a common mistake where students at times forget to simplify expressions after differentiation. For example, they might write 9x² + 0 instead of just 9x².

 

Simplifying expressions ensures clarity and correctness.

Mistake 5

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Misapplying rules to non-polynomial functions

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Students often apply polynomial rules to non-polynomial functions. This happens when they confuse terms. For example, incorrectly applying the power rule to a trigonometric function instead of a polynomial.

 

To fix this error, ensure the function type is identified correctly before applying rules.

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Examples Using the Derivative of 3x³

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Problem 1

Calculate the derivative of (3x³·4x²)

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Here, we have f(x) = 3x³·4x². Using the product rule, f'(x) = u′v + uv′ In the given equation, u = 3x³ and v = 4x². Let’s differentiate each term, u′= d/dx (3x³) = 9x² v′= d/dx (4x²) = 8x Substituting into the given equation, f'(x) = (9x²)(4x²) + (3x³)(8x) Let’s simplify terms to get the final answer, f'(x) = 36x^4 + 24x^4 Thus, the derivative of the specified function is 60x^4.

Explanation

We find the derivative of the given function by dividing the function into two parts.

The first step is finding its derivative and then combining them using the product rule to get the final result.

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Problem 2

A company manufactures boxes, and the volume of each box is represented by the function V = 3x³, where V is the volume in cubic units and x is the side length in units. If x = 2 units, calculate the rate of change of the volume.

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We have V = 3x³ (volume of the box)...(1) Now, we will differentiate the equation (1) Take the derivative of 3x³: dV/dx = 9x² Given x = 2 units (substitute this into the derivative) dV/dx = 9(2)² dV/dx = 9(4) = 36 Hence, we get the rate of change of the volume at x = 2 units as 36 cubic units per unit length.

Explanation

We find the rate of change of the volume at x = 2 units as 36, which means that at this point, the volume of the box increases by 36 cubic units per unit increase in side length.

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Problem 3

Derive the second derivative of the function y = 3x³.

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The first step is to find the first derivative, dy/dx = 9x²...(1)

Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx [9x²] d²y/dx² = 18x

Therefore, the second derivative of the function y = 3x³ is 18x.

Explanation

We use a step-by-step process, where we start with the first derivative.

Using the basic rules of differentiation, we find the first derivative and then differentiate again to find the second derivative.

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Problem 4

Prove: d/dx ((3x³)²) = 18x²·9x².

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Let’s start using the chain rule: Consider y = (3x³)² To differentiate, we use the chain rule: dy/dx = 2(3x³) * d/dx [3x³] Since the derivative of 3x³ is 9x², dy/dx = 2(3x³) * 9x² dy/dx = 18x² * 9x² Hence proved.

Explanation

In this step-by-step process, we used the chain rule to differentiate the equation.

Then, we replace 3x³ with its derivative.

As a final step, we substitute back to derive the equation.

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Problem 5

Solve: d/dx (3x³/x)

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To differentiate the function, we use the quotient rule: d/dx (3x³/x) = (d/dx (3x³) * x - 3x³ * d/dx(x)) / x² We will substitute d/dx (3x³) = 9x² and d/dx (x) = 1 = (9x² * x - 3x³ * 1) / x² = (9x³ - 3x³) / x² = 6x² / x² = 6 Therefore, d/dx (3x³/x) = 6.

Explanation

In this process, we differentiate the given function using the product rule and quotient rule.

As a final step, we simplify the equation to obtain the final result.

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FAQs on the Derivative of 3x³

1.Find the derivative of 3x³.

Using the power rule on 3x³ gives: d/dx (3x³) = 9x².

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2.Can we use the derivative of 3x³ in real life?

Yes, we can use the derivative of 3x³ in real life for calculating the rate of change of volumes, profits, and many other applications in fields such as engineering and economics.

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3.Is it possible to take the derivative of 3x³ at x = 0?

Yes, x = 0 is within the domain of 3x³, and the derivative at this point is 0.

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4.What rule is used to differentiate 3x³/x?

We use the quotient rule to differentiate 3x³/x: d/dx (3x³/x) = (x * 9x² - 3x³ * 1) / x² = 6.

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5.Are the derivatives of 3x³ and 3x⁻³ the same?

No, they are different. The derivative of 3x³ is 9x², while the derivative of 3x⁻³ is -9/x⁴.

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Important Glossaries for the Derivative of 3x³

  • Derivative: The derivative of a function indicates how the given function changes in response to a slight change in x.

 

  • Power Rule: A fundamental rule for differentiating functions of the form xⁿ, where n is a constant.

 

  • Constant Multiple Rule: A rule that states the derivative of a constant times a function is the constant times the derivative of the function.

 

  • Product Rule: A rule used to find the derivative of the product of two functions.

 

  • Quotient Rule: A rule used to find the derivative of the division of two functions.
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Jaskaran Singh Saluja

About the Author

Jaskaran Singh Saluja is a math wizard with nearly three years of experience as a math teacher. His expertise is in algebra, so he can make algebra classes interesting by turning tricky equations into simple puzzles.

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Fun Fact

: He loves to play the quiz with kids through algebra to make kids love it.

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