Last updated on September 2, 2025
We use the derivative of 5/x, which is -5/x², as a measuring tool for how the 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 5/x in detail.
We now understand the derivative of 5/x.
It is commonly represented as d/dx (5/x) or (5/x)', and its value is -5/x².
The function 5/x has a clearly defined derivative, indicating it is differentiable within its domain.
The key concepts are mentioned below:
Function: 5/x is a basic rational function.
Power Rule: Rule for differentiating xn.
Negative Exponent: Using x-1 to represent 1/x.
The derivative of 5/x can be denoted as d/dx (5/x) or (5/x)'.
The formula we use to differentiate 5/x is: d/dx (5/x) = -5/x² (or) (5/x)' = -5/x².
The formula applies to all x where x ≠ 0.
We can derive the derivative of 5/x using proofs.
To show this, we will use algebraic manipulation along with the rules of differentiation.
There are several methods we use to prove this, such as:
By First Principle
Using Power Rule
Using Quotient Rule
We will now demonstrate that the differentiation of 5/x results in -5/x² using the above-mentioned methods:
By First Principle
The derivative of 5/x can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient.
To find the derivative of 5/x using the first principle, we will consider f(x) = 5/x.
Its derivative can be expressed as the following limit. f'(x) = limₕ→₀ [f(x + h) - f(x)] / h … (1)
Given that f(x) = 5/x, we write f(x + h) = 5/(x + h).
Substituting these into equation (1), f'(x) = limₕ→₀ [5/(x + h) - 5/x] / h = limₕ→₀ [5x - 5(x + h)] / [h(x)(x + h)] = limₕ→₀ [-5h] / [h(x)(x + h)] = limₕ→₀ [-5] / [x(x + h)] = -5/x²
Hence, proved.
Using Power Rule
To prove the differentiation of 5/x using the power rule, We rewrite the function as: 5/x = 5x-1.
Using the power rule, if y = xn, then dy/dx = nx(n-1).
So we get, d/dx (5x-1) = 5(-1)x(-1-1) = -5x-2.
Therefore, d/dx (5/x) = -5/x².
Using Quotient Rule
We will now prove the derivative of 5/x using the quotient rule.
The step-by-step process is demonstrated below:
Here, we use the formula, 5/x = 5 * (1/x).
Given that u = 5 and v = x⁻¹,
Using the quotient rule formula: d/dx [u/v] = [u'v - uv']/v². u' = 0 (since u = 5 is a constant) v' = d/dx (x⁻¹) = -x⁻² (substitute v = x⁻¹).
Using the quotient rule, d/dx (5/x) = [0 * x⁻¹ - 5 * (-x⁻²)] / (x⁻¹)² = (5x⁻²)/x⁻² = -5/x².
Hence, d/dx (5/x) = -5/x².
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 5/x.
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 5/x, 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).
When x is 0, the derivative is undefined because 5/x is undefined at this point. When x is positive or negative, the derivative of 5/x = -5/x², indicating a negative slope.
Students frequently make mistakes when differentiating 5/x. These mistakes can be resolved by understanding the proper solutions. Here are a few common mistakes and ways to solve them:
Calculate the derivative of (5/x · x²).
Here, we have f(x) = (5/x) · x².
Simplifying, f(x) = 5x.
The derivative of a constant times x is simply that constant.
Thus, f'(x) = 5.
Thus, the derivative of the specified function is 5.
We find the derivative of the given function by simplifying it first. The first step is finding its derivative, and since it simplifies to a linear function, we directly obtain the derivative.
A company is tracking its cost per unit, which is represented by the function c(x) = 5/x, where x is the number of units produced. If x = 10 units, find the rate of change of the cost per unit.
We have c(x) = 5/x (cost per unit)...(1)
Now, we will differentiate the equation (1).
Take the derivative 5/x: dc/dx = -5/x².
Given x = 10, substitute this into the derivative: dc/dx = -5/(10)² dc/dx = -5/100 = -0.05.
Hence, the rate of change of the cost per unit at x = 10 is -0.05.
We find the rate of change of the cost per unit at x = 10 as -0.05, which indicates that the cost per unit decreases as the number of units produced increases.
Derive the second derivative of the function y = 5/x.
The first step is to find the first derivative, dy/dx = -5/x²...(1)
Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx [-5/x²]
Here we use the power rule, d²y/dx² = 10/x³.
Therefore, the second derivative of the function y = 5/x is 10/x³.
We use the step-by-step process, where we start with the first derivative. Using the power rule, we differentiate -5/x². We then simplify the terms to find the final answer.
Prove: d/dx (1/x²) = -2/x³.
Let’s start using the power rule:
Consider y = 1/x².
We can write it as y = x⁻².
To differentiate, we use the power rule: dy/dx = -2x⁻³.
Substituting y = 1/x², d/dx (1/x²) = -2/x³.
Hence proved.
In this step-by-step process, we used the power rule to differentiate the equation. Then, we replace x⁻² with its derivative. As a final step, we substitute the identity to derive the equation.
Solve: d/dx ((5/x)/x).
To differentiate the function, we use the quotient rule: d/dx ((5/x)/x) = (d/dx (5/x) · x - (5/x) · d/dx(x))/x².
We will substitute d/dx (5/x) = -5/x² and d/dx (x) = 1: ((-5/x²) · x - (5/x) · 1)/x² = (-5/x - 5/x)/x² = -10/x³.
Therefore, d/dx ((5/x)/x) = -10/x³.
In this process, we differentiate the given function using the quotient rule. As a final step, we simplify the equation to obtain the final result.
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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