Chapter 3: Problem 27
Differentiate the function. \(f(x)=k(a-x)(b-x)\)
Short Answer
Expert verified
The derivative is \( f'(x) = k(2x - (a+b)) \).
Step by step solution
01
Expand the Function
The first step is to expand the given function before differentiating. The function is \( f(x) = k(a-x)(b-x) \). Use the distributive property to expand it.\[ f(x) = k((a-x)(b-x)) = k((ab - xb - xa + x^2)) = k(x^2 - (a + b)x + ab) \]
02
Differentiate the Expanded Function
Now, differentiate the expanded function term by term with respect to \( x \). The function is \( f(x) = k(x^2 - (a+b)x + ab) \).To differentiate: 1. Apply the power rule to \( x^2 \).2. Apply the constant multiplication rule.The derivative is:\[ f'(x) = k(2x - (a+b)) \]
03
Simplify the Derivative
In this last step, simplify the expression for the derivative if necessary. The expression we derived is already simplified: \[ f'(x) = k(2x - (a+b)) \]This is the final derivative of the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Expanded Function
When we talk about expanding a function, we're essentially looking to transform it into a more manageable form for operations like differentiation. In our example, the function is \( f(x) = k(a-x)(b-x) \).
Expanding means using algebraic manipulation to simplify or reorganize it.
Here's how we do it:
This step is crucial because differentiating simple terms is much easier than handling complex expressions.
Expanding means using algebraic manipulation to simplify or reorganize it.
Here's how we do it:
- Take the expression \( (a-x)(b-x) \) and apply the distributive property.
- This means multiplying each term within the first set of parentheses by each term in the second set, resulting in \( ab - xb - xa + x^2 \).
This step is crucial because differentiating simple terms is much easier than handling complex expressions.
Power Rule
The power rule is a fundamental differentiation technique used to find the derivative of terms of the form \( x^n \). For any real number \( n \), the power rule states:
For \( y = x^n \), the derivative \( y' = nx^{n-1} \).
Applying this concept, in our example:
Remember, if you have a constant in front (like in our function, where 2 is multiplied by \( x \)), it remains in the final derivative.
For \( y = x^n \), the derivative \( y' = nx^{n-1} \).
Applying this concept, in our example:
- The term \( x^2 \) in the expanded function becomes \( 2x^{2-1} = 2x \) when derived.
Remember, if you have a constant in front (like in our function, where 2 is multiplied by \( x \)), it remains in the final derivative.
Distributive Property
The distributive property is an algebraic rule that allows us to multiply a single term by a set of terms added together and distribute the multiplication over each term individually. In essence, for terms \( a, b, c \), and \( d \):
\( a(b+c) = ab + ac \)
In the context of our function, we applied this to \( (a-x)(b-x) \):
The distributive property helps us unravel complex expressions into simpler pieces.
\( a(b+c) = ab + ac \)
In the context of our function, we applied this to \( (a-x)(b-x) \):
- Multiplied \( (a-x) \) by each term in \( (b-x) \).
- This produced the expanded form \( ab - xb - xa + x^2 \).
The distributive property helps us unravel complex expressions into simpler pieces.
Constant Multiplication Rule
The constant multiplication rule in differentiation is simple yet powerful.
It states that if you have a constant multiplied by a function, the derivative of the whole function is simply the constant multiplied by the derivative of the function. Mathematically:
If \( y = c \, g(x) \), then \( y' = c \, g'(x) \).
In our function \( f(x) = k(x^2 - (a+b)x + ab) \):
It states that if you have a constant multiplied by a function, the derivative of the whole function is simply the constant multiplied by the derivative of the function. Mathematically:
If \( y = c \, g(x) \), then \( y' = c \, g'(x) \).
In our function \( f(x) = k(x^2 - (a+b)x + ab) \):
- Each term that we derived from applying the power rule is multiplied by the constant \( k \).
- The derivative becomes \( f'(x) = k(2x - (a+b)) \).