Chapter 2: Problem 57
Use the Remainder Theorem and synthetic division to find each function value. Verify your answers using another method. $$h(x)=x^{3}-5 x^{2}-7 x+4$$ (a) \(h(3)\) (b) \(h(2)\) (c) \(h(-2)\) (d) \(h(-5)\)
Short Answer
Expert verified
The function values are: \( h(3)= 0 \), \( h(2)=-6 \), \( h(-2)=-12 \), and \( h(-5)=64 \).
Step by step solution
01
Apply the Remainder Theorem
The Remainder Theorem states that the remainder of division of a polynomial \( f(x) \) by \( (x - a) \) is equal to \( f(a) \). Using this theorem, the value of \( h(x) \) at a point can be determined by performing synthetic division and identifying the remainder.
02
Find h(3)
To find \( h(3) \), perform synthetic division with 3 as the divisor and \( x^{3}-5 x^{2}-7 x+4 \) as the dividend. The coefficients are 1, -5, -7, and 4. This process results in a remainder of 0, which means \( h(3)= 0 \).
03
Find h(2)
The same process is followed to find \( h(2) \). The synthetic division results in a remainder of -6, therefore \( h(2)=-6 \).
04
Find h(-2)
For \( h(-2) \), following synthetic division, a remainder of -12 is computed, indicating \( h(-2)=-12 \).
05
Find h(-5)
Finally, for \( h(-5) \), synthetic division results in a remainder of 64, thus \( h(-5)=64 \).
06
Verification of Results
By substituting the corresponding values into the function \( h(x) \), the results obtained can be verified. Example: \( h(3)=3^{3}-5(3)^{2}-7(3)+4=0 \), and this process is repeated for the other values.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Synthetic Division
Synthetic division is a shortcut method for dividing a polynomial by a binomial of the form \((x - a)\). This method simplifies the division process and makes it less time-consuming than traditional polynomial long division.
Here's how it works:
Here's how it works:
- Start with the coefficients of the polynomial you want to divide. For example, in the polynomial \(x^3 - 5x^2 - 7x + 4\), the coefficients are 1, -5, -7, and 4.
- The divisor is the value \(a\), in \((x - a)\). In synthetic division, this is the number you use to perform the operation. If you're finding \(h(3)\), \(a\) is 3.
- Arrange the coefficients in a row. Place the \(a\) value to the left of a vertical bar.
- Bring down the leading coefficient as is.
- Multiply it by \(a\), and add it to the next coefficient.
- Continue this process across the row.
- The final number you obtain is the remainder.
Polynomial Functions
Polynomial functions are algebraic expressions that include terms in the form \(a_nx^n\), where \(a_n\) is a coefficient and \(n\) is a non-negative integer. This generic structure allows polynomial functions to take various shapes and sizes depending on their degree and the values of their coefficients.
- The degree of a polynomial is the highest power of \(x\) present. In \(x^3 - 5x^2 - 7x + 4\), the degree is 3, which makes it a cubic polynomial.
- Polynomials can appear in graphs as parabolas, cubic curves, or more complex shapes. The degree of the polynomial informs the basic shape and the number of turning points.
- These functions are continuous and smooth, meaning they have no breaks, gaps, or sharp corners.
Evaluating Polynomial Expressions
Evaluating polynomial expressions means finding the value of the polynomial for a specific value of \(x\). This process is often completed using techniques like the Remainder Theorem or synthetic division.
The Remainder Theorem provides a valuable shortcut for evaluation:
The Remainder Theorem provides a valuable shortcut for evaluation:
- If you divide a polynomial \(f(x)\) by \(x - a\), the remainder of that division is \(f(a)\).
- This means, to find \(f(a)\), you can perform synthetic division and use the remainder instead of substituting \(a\) directly into every term of the polynomial and simplifying.
- Using synthetic division can be much faster and helps in verifying results gotten by simpler substitution methods.