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Problem:
Factor [tex][tex]$x^2 + 7x + 12$[/tex][/tex].

Solution:
We are looking for an answer that is the product of two binomials in parentheses:
[tex]
(x + \text{ }(x + \text{ )}
[/tex]

Label [tex]b[/tex] and [tex]c[/tex].
[tex]
\begin{array}{l}
b = \square \\
c = \square
\end{array}
[/tex]

Since we know that [tex]m + n = b[/tex] and [tex]mn = c[/tex], we need to find two numbers that multiply to 12 and add to 7. Start by making a list of all possible ways to multiply two numbers to get 12. Then, find the pair that also adds to 7. Once you find the pair that works, you can stop—you don't have to list every option if you've already found the correct one.

[tex]
\begin{array}{l}
12 \cdot 1 = 12 \quad \text{and} \quad 12 + 1 = 13 \\
6 \cdot 2 = 12 \quad \text{and} \quad 6 + 2 = 8 \\
3 \cdot 4 = 12 \quad \text{and} \quad 3 + 4 = 7
\end{array}
[/tex]

So our two numbers are 3 and 4. We write our answer as the two factors:
[tex]
(x + 4)(x + 3)
[/tex]

So, the two factors of [tex][tex]$x^2 + 7x + 12$[/tex][/tex] are [tex][tex]$(x + 4)(x + 3)$[/tex][/tex]. Again, we can always check our answer by multiplying the two binomials back together.

Did you notice anything about the answers to the previous two examples? We were factoring expressions whose [tex]b[/tex] and [tex]c[/tex] values were both positive. What did you notice about both of your factors of these types of expressions? Were they both positive? Were there any negatives at all?

When [tex]a = 1[/tex] and both [tex]b[/tex] and [tex]c[/tex] are positive, your two numbers, [tex]m[/tex] and [tex]n[/tex], will also be positive. Remembering this pattern will help you narrow down the possible choices.


Sagot :

To factor the polynomial [tex]\(x^2 + 7x + 12\)[/tex], we need to find two binomials whose product equals the given polynomial.

We start with the form:
[tex]\[ (x + a)(x + b) \][/tex]
Expanding this product, we get:
[tex]\[ (x + a)(x + b) = x^2 + (a + b)x + ab \][/tex]
By comparing this with the original polynomial [tex]\(x^2 + 7x + 12\)[/tex], we can see that:
[tex]\[ a + b = 7 \quad \text{and} \quad ab = 12 \][/tex]

Our task is to find two numbers, [tex]\(a\)[/tex] and [tex]\(b\)[/tex], that satisfy these conditions. Let's list pairs of numbers that multiply to 12 and check their sum:

[tex]\[ \begin{array}{l} 1 \cdot 12 = 12 \quad \text{and} \quad 1 + 12 = 13 \\ 2 \cdot 6 = 12 \quad \text{and} \quad 2 + 6 = 8 \\ 3 \cdot 4 = 12 \quad \text{and} \quad 3 + 4 = 7 \\ \end{array} \][/tex]

Among these pairs, the pair that both multiplies to 12 and adds to 7 is [tex]\(3\)[/tex] and [tex]\(4\)[/tex]. Therefore, we have identified [tex]\(a = 3\)[/tex] and [tex]\(b = 4\)[/tex].

Thus, the factored form of the polynomial [tex]\(x^2 + 7x + 12\)[/tex] is:
[tex]\[ (x + 3)(x + 4) \][/tex]

We can always verify our solution by expanding the factors back out:
[tex]\[ (x + 3)(x + 4) = x^2 + 4x + 3x + 12 = x^2 + 7x + 12 \][/tex]

Since this matches the original polynomial, our factorization is confirmed correct. Therefore, the factored form of [tex]\(x^2 + 7x + 12\)[/tex] is:
[tex]\[ (x + 3)(x + 4) \][/tex]