Chapter 5: Problem 85
Find the value of \(c\) that makes each trinomial a perfect square trinomial. $$ m^{2}-14 m+c $$
Short Answer
Expert verified
The value of \( c \) is 49.
Step by step solution
01
Understanding a Perfect Square Trinomial
A perfect square trinomial is a polynomial that can be written in the form \( (a+b)^2 = a^2 + 2ab + b^2 \), or \( (a-b)^2 = a^2 - 2ab + b^2 \). The given trinomial is \( m^2 - 14m + c \). We need to find the value of \( c \) so that it fits this pattern.
02
Identifying the middle term
The middle term of the trinomial, \( -14m \), is compared with \(-2ab \) (from \( (a-b)^2 = a^2 - 2ab + b^2 \)). Here, \(-2ab = -14m \), which implies \( a = m \) and \( 2b = 14 \).
03
Solving for b
To solve for \( b \), we set \( 2b = 14 \). Dividing both sides by 2 gives \( b = 7 \).
04
Calculating the value of c
We know that \( c = b^2 \) for the trinomial to be a perfect square. Substituting \( b = 7 \) gives us \( c = 7^2 = 49 \).
05
Verifying the result
To verify, substitute \( c = 49 \) back into the original trinomial and check. The trinomial becomes \( m^2 - 14m + 49 \), which can be written as \( (m - 7)^2 \), confirming our solution that the trinomial is indeed a perfect square.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Trinomial
A trinomial is a type of polynomial that consists of three distinct terms. It is expressed in the general form as \( ax^2 + bx + c \). In the given exercise, our trinomial is \( m^2 - 14m + c \), where:
- \( a \) represents the coefficient of \( m^2 \), which is 1.
- \( b \) is the coefficient of the middle term, \(-14\).
- \( c \) is our constant term.
Middle Term
The middle term of a polynomial plays a crucial role in identifying its properties and eventual transformation into a perfect square trinomial. In our example, the middle term is \(-14m\). This term is significant because it provides us with critical information about the other values in the trinomial.For a trinomial to be a perfect square, it should match the expanded form \((a-b)^2 = a^2 - 2ab + b^2\). The middle term equivalent \(-2ab\) in this pattern allows us to link the value of \(-14m\) to find the relationship between \( a \) and \( b \), knowing that in our example, \( a = m \) and thus establishing \(-2b = -14\).
Solving for b
To solve for \( b \), let's start with the equation derived from our middle term: \(-2b = -14\). This relationship comes from matching the middle term of the expanded binomial square. Solving for \( b \) involves straightforward algebraic manipulation:
- First, you set up the equation: \( 2b = 14 \).
- Divide both sides by 2: \( b = \frac{14}{2} \).
- Calculate the division: \( b = 7 \).
Verifying the Result
Verification is an essential step in confirming our calculations and ensuring that we have indeed transformed the trinomial into a perfect square trinomial. With the value \( b = 7 \), we find \( c \) using the equation \( c = b^2 \).
- Substitute the value of \( b \): \( c = 7^2 \).
- Calculate the square: \( c = 49 \).
- The expression becomes \( m^2 - 14m + 49 \).
- This can be factored into \((m - 7)^2\).