Chapter 4: Problem 46
\(39-51\) . Use synthetic division and the Remainder Theorem to evaluate \(P(c) .\) $$ P(x)=6 x^{5}+10 x^{3}+x+1, \quad c=-2 $$
Short Answer
Expert verified
The value of \( P(-2) \) is \(-273\).
Step by step solution
01
Organize Coefficients
Write down the coefficients of the polynomial \( P(x) = 6x^5 + 0x^4 + 10x^3 + 0x^2 + x + 1 \). These are \([6, 0, 10, 0, 1, 1]\). Note the coefficients for terms with zero coefficients are included.
02
Set Up Synthetic Division
To use synthetic division with \(c = -2\), write \(-2\) outside a division-like symbol and place the coefficients \([6, 0, 10, 0, 1, 1]\) inside.
03
Perform Synthetic Division
Start the synthetic division by bringing down the first coefficient, which is 6. Multiply this 6 by \(-2\) and write the result under the next coefficient. Add this result to the coefficient above it. Continue this process:1. Bring down the 6.2. \( -2 \times 6 = -12 \) (write under 0).3. \( 0 + (-12) = -12 \).4. \( -2 \times -12 = 24 \) (write under 10).5. \( 10 + 24 = 34 \).6. \( -2 \times 34 = -68 \) (write under 0).7. \( 0 + (-68) = -68 \).8. \( -2 \times -68 = 136 \) (write under 1).9. \( 1 + 136 = 137 \).10. \( -2 \times 137 = -274 \) (write under last 1).11. \( 1 - 274 = -273 \).The result of synthetic division is: \([6, -12, 34, -68, 137, -273]\).
04
Interpret the Remainder
The remainder of the division, \(-273\), corresponds to \(P(c)\) where \(c = -2\). According to the Remainder Theorem, this is the value of \(P(-2)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Coefficients
Polynomial coefficients are the numbers in front of the variables in a polynomial expression. For a given polynomial like \( P(x) = 6x^5 + 10x^3 + x + 1 \), each term has a coefficient which dictates the term's "weight" or influence on the polynomial. Coefficients can be zero, which means the corresponding term is absent.
- The coefficients in our polynomial are: \([6, 0, 10, 0, 1, 1]\).
- Note the zeroes for the \(x^4\) and \(x^2\) terms, indicating their absence.
Remainder Theorem
The Remainder Theorem is a handy tool in polynomial division. It states that the remainder of the division of a polynomial \(P(x)\) by a linear divisor \(x - c\) is equivalent to \(P(c)\), the value of the polynomial evaluated at \(c\). This means that once you perform synthetic division and obtain a remainder, you have directly found \(P(c)\).
- In our example, dividing \(P(x)\) by \(x + 2\) yields a remainder.
- The remainder \(-273\) is \(P(-2)\).
Polynomial Evaluation
Polynomial evaluation involves finding the result of a polynomial expression for a specific value of the variable. When given \(P(x) = 6x^5 + 10x^3 + x + 1\) and asked to evaluate at \(x = -2\), we substitute \(-2\) for \(x\) and compute the outcome. Synthetic division aids this process by breaking down the polynomial using its coefficients.
- The synthetic division method streamlines this evaluation.
- Manual substitution would be tedious for higher degrees.
Division Algorithm in Algebra
The division algorithm in algebra refers to the procedure of dividing one polynomial by another to yield a quotient and a remainder. This is similar to long division in arithmetic. Synthetic division is a shortcut for the division algorithm specifically designed when dividing by a linear factor. The algorithm breaks down as follows:
In practice, synthetic division simplifies operations dramatically over the classic polynomial long division, focusing computational ease and speed.
- Arrange the polynomial with all coefficients, including zero coefficients.
- Use the root of the divisor \(x - c\) as the synthetic division number.
- Consistently perform arithmetic to simplify and deduce the quotient and remainder.
In practice, synthetic division simplifies operations dramatically over the classic polynomial long division, focusing computational ease and speed.