Chapter 1: Problem 74
Factor the trinomial. $$2(a+b)^{2}+5(a+b)-3$$
Short Answer
Expert verified
The factorization is \((2(a+b) - 1)((a+b) + 3)\).
Step by step solution
01
Identify the Variable Replacement
Notice that the expression contains \((a+b)\) repeated. We can simplify our work by setting \(x = a+b\). This makes our expression \(2x^2 + 5x - 3\).
02
List Potential Factor Pairs
We want to factor \(2x^2 + 5x - 3\) into the form \((mx+n)(px+q)\). The coefficient of the quadratic term is 2 and the constant term is -3. We need factor pairs which when multiplied give us \(2 \times (-3) = -6\). Possible factor pairs of -6 are: (-1, 6), (1, -6), (-2, 3), and (2, -3).
03
Choose the Correct Factor Pair
We need to find a pair that sums up to the middle coefficient, 5. Specifically, solve for \(m \times q + n \times p = 5\): - The correct pair is (-1, 6), leading to the expression: \((2x - 1)(x + 3)\).Verify that this factorization is correct by expanding: \((2x - 1)(x + 3) = 2x^2 + 6x - x - 3 = 2x^2 + 5x - 3\).
04
Substitute Back the Original Variable
We originally set \(x = a + b\). Now that we have factored \(2x^2 + 5x - 3\) into \((2x - 1)(x + 3)\), substitute back \( a + b \). Replace to get \( (2(a+b) - 1)((a+b) + 3) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Variable Substitution
Variable substitution is a helpful technique in simplifying complex algebraic expressions. When presented with an expression that includes repetitive parts, like \(2(a+b)^{2}+5(a+b)-3\), it's beneficial to substitute the repeating element with a single variable.
This step transforms a potentially complicated expression into a simpler form. For example:
This step transforms a potentially complicated expression into a simpler form. For example:
- Identify the repetitive expression, \(a + b\), in this exercise.
- Substitute with a new variable, say \(x = a + b\).
Quadratic Trinomials
Quadratic trinomials are polynomial expressions of the form \(ax^2 + bx + c\). The key to working with these is to factor them, which means expressing them as a product of two binomials. In the exercise, \(2x^2 + 5x - 3\) is the quadratic trinomial.
To factor a quadratic trinomial:
To factor a quadratic trinomial:
- Examine the coefficients: here, 2, 5, and -3.
- Multiply the leading coefficient (2) and the constant (-3) to form -6.
Factorization Verification
After attempting to factorize a quadratic trinomial, it’s critical to verify the solution. Verification ensures that the factorization is correct. In the exercise, we deduced the factorization of \(2x^2 + 5x - 3\) as \((2x - 1)(x + 3)\).
To verify:
To verify:
- Expand the factorized form to see if it matches the original expression.
- Use the distributive property: \( (2x - 1)(x + 3) = 2x^2 + 6x - x - 3\).
- Simplify it to \(2x^2 + 5x - 3\), confirming it equals the initial trinomial.