Chapter 4: Problem 50
Find the value of each polynomial for \((a) x=2\) and \((b) x=-1\) \(x^{4}-6 x^{3}+x^{2}-x\)
Short Answer
Expert verified
For \(x = 2\), the value is -30. For \(x = -1\), the value is 9.
Step by step solution
01
Understand the polynomial
The given polynomial is \(x^{4} - 6x^{3} + x^{2} - x\). We need to find its value for two different values of \(x\): 2 and -1.
02
Substitute \(x = 2\)
Replace \(x\) with 2 in the polynomial: \((2)^{4} - 6(2)^{3} + (2)^{2} - (2)\).
03
Simplify the expression for \(x = 2\)
Calculate each term separately and then combine them: \[(2)^{4} = 16\]\[-6(2)^{3} = -6(8) = -48\]\[(2)^{2} = 4\]\[-(2) = -2\]Add them together: \[16 - 48 + 4 - 2 = -30\]
04
Result for \(x = 2\)
The value of the polynomial for \(x = 2\) is -30.
05
Substitute \(x = -1\)
Replace \(x\) with -1 in the polynomial: \((-1)^{4} - 6(-1)^{3} + (-1)^{2} - (-1)\).
06
Simplify the expression for \(x = -1\)
Calculate each term separately and then combine them: \[(-1)^{4} = 1\]\[-6(-1)^{3} = -6(-1) = 6\]\[(-1)^{2} = 1\]\[-(-1) = 1\]Add them together: \[1 + 6 + 1 + 1 = 9\]
07
Result for \(x = -1\)
The value of the polynomial for \(x = -1\) is 9.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial
A polynomial is a mathematical expression involving a sum of powers in one or more variables multiplied by coefficients. In simpler terms, it's like a multivariable equation. Here we have a polynomial in the variable, denoted by the expression: \(x^{4} - 6x^{3} + x^{2} - x\). This polynomial has four terms:
- \(x^{4}\)
- \(-6x^{3}\)
- \(x^{2}\)
- \(-x\)
Substitution
Substitution simply means replacing the variable in the polynomial with a given value. To find the value of the polynomial \(x^{4} - 6x^{3} + x^{2} - x\) for \(x = 2\), we replace every instance of \(x\) with 2. The modified polynomial becomes: \((2)^{4} - 6(2)^{3} + (2)^{2} - (2)\). Similarly, for \(x = -1\), we substitute -1 for every \(x\) in the polynomial, resulting in \((-1)^{4} - 6(-1)^{3} + (-1)^{2} - (-1)\). This step is crucial as it sets up the polynomial for further calculations.
Simplification
Simplification involves calculating and combining all the terms in the polynomial. For \(x = 2\), we calculate:
- \((2)^{4} = 16\)
- \(-6(2)^{3} = -48\)
- \((2)^{2} = 4\)
- \(-2\)
- \((-1)^{4} = 1\)
- \(-6(-1)^{3} = 6\)
- \((-1)^{2} = 1\)
- \(-(-1) = 1\)
Exponents
Exponents are an important part of polynomials. An exponent tells us how many times a number (the base) is multiplied by itself. For example:
- \((2)^{4}\) means \(2\times2\times2\times2 = 16\)
- \((-1)^{4}\) means \(-1\times-1\times-1\times-1 = 1\)
- \((2)^{3}\) means \(2\times2\times2 = 8\)
- \((-1)^{2}\) means \(-1\times-1 = 1\)