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Assume \(h \neq 0 .\) Compute and simplify the difference quotient $$ \frac{f(x+h)-f(x)}{h} $$ $$f(x)=x-x^{2}$$

Short Answer

Expert verified
Answer: The simplified difference quotient for the function \(f(x)=x-x^2\) is \(x^2 - 2x - h\).

Step by step solution

01

Write down the difference quotient with the given function

We are given the function \(f(x)=x-x^2\) and the difference quotient is \(\frac{f(x+h)-f(x)}{h}\). So we need to plug this function into the expression and compute the quotient.
02

Substitute the function into the difference quotient

Now we will substitute the function \(f(x)\) into the difference quotient formula: $$ \frac{f(x+h)-f(x)}{h} = \frac{(x+h)-(x+h)^2 - (x-x^2)}{h} $$
03

Expand the expression and simplify the numerator

We will expand the expression in the numerator and simplify it. This will help us to cancel out some terms and make it easier to find the result: $$ \frac{(x+h)-(x^2+2xh+h^2) - (x-x^2)}{h} = \frac{x^2 - 2xh - h^2}{h} $$
04

Cancel out the common factor of h

In this step, we notice that the numerator has a common factor of \(h\) in each term. We can cancel out this common factor with the denominator to simplify the expression: $$ \frac{x^2 - 2xh - h^2}{h} = \frac{h(x^2 - 2x - h)}{h} = x^2 - 2x - h $$
05

Write down the final result

Finally, we have simplified the difference quotient for the given function \(f(x)=x-x^2\): $$ \frac{f(x+h)-f(x)}{h} = x^2 - 2x - h $$

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Simplification
Simplification in mathematics is the process of reducing expressions to their simplest form. This involves combining like terms, canceling common factors, and performing basic arithmetic operations. Simplification makes expressions easier to understand and work with. For the difference quotient, simplification is crucial, because it helps in analyzing and extracting meaningful information about the given function.

When simplifying, always look for:
  • Like terms: Terms that have the same variable part, such as combining terms with \( x \) or \( x^2 \).
  • Common factors: Factors that appear in every term of an expression, like the \( h \) in both the numerator and the denominator in the difference quotient.

In the provided solution, simplification was key in reducing the expression from a complex fraction to something more straightforward. This simplification is important for making calculus problems more manageable and less prone to error.
Polynomial Functions
Polynomial functions are mathematical expressions involving a sum of powers in one or more variables multiplied by coefficients. The general form of a polynomial function in one variable is:

\[ f(x) = a_nx^n + a_{n-1}x^{n-1} + ... + a_1x + a_0 \]

where \( a_n, a_{n-1}, ..., a_1, a_0 \) are constants, and \( n \) is a non-negative integer.

Polynomial functions are important because they are simple, smooth, and well-behaved, making them easy to work with and a central idea in calculus and algebra. The given function \( f(x) = x - x^2 \) is a polynomial of degree 2, known as a quadratic polynomial. It is characterized by a power of 2 as the highest exponent.

When working with polynomial functions, we are often interested in:
  • Expanding expressions: As seen in step 3, expanding \((x+h)^2\) was necessary to simplify the expression.
  • Manipulating them: Factoring or expanding polynomials is a frequent exercise when dealing with equations and derivative computations.
Calculus
Calculus is a branch of mathematics focused on limits, functions, derivatives, integrals, and infinite series. It provides the framework for modeling systems in which change is a key concept. The difference quotient is a fundamental idea in calculus, used to find the derivative of a function. The derivative describes the rate of change of a function with respect to its variable.

The process of computing the difference quotient, like in the original exercise, is a stepping stone to differentiation. This process includes:
  • Substituting the function values into the difference quotient formula.
  • Simplifying the expression by expanding and canceling out terms.


The difference quotient \( \frac{f(x+h) - f(x)}{h} \) represents the slope of the secant line between two points \((x, f(x))\) and \((x+h, f(x+h))\) on the graph of \(f\). This is why simplification to remove \( h \) in the denominator is critical, as it leads to computing the derivative by taking the limit as \( h \to 0 \). The final expression \( x^2 - 2x - h \) approximates the slope of the secant, paving the way for deeper insights into the behavior of functions.

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Most popular questions from this chapter

Example \(11(b)\) showed how we create a table of values for a function when you get to choose all the values of the inputs. The technique presented does not work for Casio calculators. This exercise is designed for users of Casio calculators. \(\cdot \quad\) Enter an equation such as \(y=x^{3}-2 x+3\) in the equation memory. This can be done by selecting TABLE in the MAIN menu. \- Return to the MAIN menu and select LIST. Enter the numbers at which you want to evaluate the function as List 1 \(\cdot \quad\) Return to the MAIN menu and select TABLE. Then press SET-UP [that is, 2nd MENU] and select LIST as the Variable; on the LIST menu, choose List 1. Press EXIT and then press TABL to produce the table. \- Use the up/down arrow key to scroll through the table. If you change an entry in the X column, the corresponding \(y_{1}\) value will automatically change. (a) Use this technique to duplicate the table in Example \(11(\mathrm{b})\) (b) Change the number -11 to \(10,\) and confirm that you've obtained \(10^{3}-2(10)+3\)

Determine the domain of the function according to the usual convention. $$h(x)=\sqrt{(x+1)^{2}}$$

Find the approximate intervals on which the function is increasing, those on which it is decreasing, and those on which it is constant. $$f(x)=\sqrt{x}$$

Write the rule of a function g whose graph can be obtained from the graph of the function \(f\) by performing the transformations in the order given. \(f(x)=x^{2}-x+1 ;\) reflect the graph in the \(x\) -axis, then shift it vertically upward 3 units.

Determine the domain of the function according to the usual convention. $$h(t)=|t|-1$$

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