Chapter 11: Problem 54
We have seen the close connection between polynomial division and writing a quotient of polynomials in lowest terms after factoring the numerator. We can also show a connection between dividing one polynomial by another and factoring the first polynomial. letting $$ f(x)=2 x^{2}+5 x-12 $$ Evaluate \(f\left(\frac{3}{2}\right)\).
Short Answer
Step by step solution
Substitute the value
Compute the squared term
Compute the linear term
Combine and simplify
Perform the addition
Subtract the constant term
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Evaluating Polynomial Functions
Here's the step-by-step process:
- Substitute \( x = \frac{3}{2} \) into the polynomial function.
Given the function is \( 2{\left(\frac{3}{2}\right)}^2 + 5\left(\frac{3}{2}\right) - 12 \). - Simplify each term separately.
First, calculate the squared term: \( \left(\frac{3}{2}\right)^2 = \frac{9}{4} \). Then, multiply by 2: \( 2 \cdot \frac{9}{4} = \frac{18}{4} = \frac{9}{2} \). - Next, compute the linear term: \( 5 \cdot \frac{3}{2} = \frac{15}{2} \).
- Combine and simplify all parts: \( f\left(\frac{3}{2}\right) = \frac{9}{2} + \frac{15}{2} - 12 \).
- Perform the additional step: \( \frac{9}{2} + \frac{15}{2} = \frac{24}{2} = 12 \).
- Finally, subtract the constant term \( 12 - 12 = 0 \).
Factoring Polynomials
Steps to factor a polynomial:
- Identify the polynomial to factor. Here, it is \( 2x^2 + 5x - 12 \).
- Find two numbers that multiply to give the product of the coefficient of \( x^2 \) term (2) and the constant term (-12), and add up to the coefficient of the \( x \) term (5).
The numbers are 8 and -3 because \( 2 \cdot (-12) = -24 \) and \( 8 + (-3) = 5 \). - Rewrite the middle term (5x) using the numbers found: \( 2x^2 + 8x - 3x - 12 \).
- Group terms to factor by grouping: \( 2x(x + 4) - 3(x + 4) \).
- Factor out the common factor from each group: \((2x - 3)(x + 4) \).
Substitution in Algebra
In the given exercise, we used substitution to find \( f\left(\frac{3}{2}\right) \) for the polynomial function \( f(x)=2x^{2}+5x-12 \).
Steps to perform substitution:
- Identify the expression or equation where substitution is needed. Here, it is \( f(x)=2x^{2}+5x-12 \).
- Replace the variable \( x \) with the given value \( \frac{3}{2} \).
- Simplify the expression step by step by performing arithmetic operations.
Compute each term separately, combine them, and simplify if needed.
Simplifying Expressions
In the given exercise, after substituting \( \frac{3}{2} \) into \( f(x)=2x^{2}+5x-12 \), we simplified the resulting expression step by step.
Steps for simplification:
- Combine all like terms. In \(\frac{9}{2} + \frac{15}{2} - 12 \), combine \(\frac{9}{2} \) and \(\frac{15}{2} \) as they are like terms (both involving \(\frac{1}{2} \)).
- Convert to a common denominator if needed to combine fractions.
Then, \( \frac{9}{2} + \frac{15}{2} = \frac{24}{2} \). - Simplify fractions and perform arithmetic operations like addition or subtraction.
Finally, \( 12 - 12 = 0 \).