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Factor each perfect square trinomial.

13. [tex]$x^2 + 6x + 9$[/tex]

16. [tex]$x^2 - 14x + 49$[/tex]

19. [tex]-4x^2 - 24x - 36$[/tex]


Sagot :

Sure! Let's factor each perfect square trinomial step-by-step.

### 13. [tex]\( x^2 + 6x + 9 \)[/tex]

To factorize this trinomial, we need to determine if it can be written as the square of a binomial.

First, we recognize if it follows the form [tex]\( a^2 + 2ab + b^2 \)[/tex], which factors to [tex]\( (a + b)^2 \)[/tex]:

Given:
[tex]\[ x^2 + 6x + 9 \][/tex]

1. Identify [tex]\(a\)[/tex] and [tex]\(b\)[/tex]:
- [tex]\(a^2 = x^2 \Rightarrow a = x\)[/tex]
- [tex]\(b^2 = 9 \Rightarrow b = 3\)[/tex]

2. Check the middle term:
- The middle term [tex]\(6x\)[/tex] should be [tex]\(2ab = 2 \cdot x \cdot 3 = 6x \)[/tex], which matches.

Therefore, we write:
[tex]\[ x^2 + 6x + 9 = (x + 3)^2 \][/tex]

So, the factorized form is:
[tex]\[ (x + 3)^2 \][/tex]

### 16. [tex]\( x^2 - 14x + 49 \)[/tex]

To factorize this trinomial, we examine if it follows the form [tex]\( a^2 - 2ab + b^2 \)[/tex], which factors to [tex]\( (a - b)^2 \)[/tex]:

Given:
[tex]\[ x^2 - 14x + 49 \][/tex]

1. Identify [tex]\(a\)[/tex] and [tex]\(b\)[/tex]:
- [tex]\(a^2 = x^2 \Rightarrow a = x\)[/tex]
- [tex]\(b^2 = 49 \Rightarrow b = 7\)[/tex]

2. Check the middle term:
- The middle term [tex]\(-14x\)[/tex] should be [tex]\(-2ab = -2 \cdot x \cdot 7 = -14x \)[/tex], which matches.

Therefore, we write:
[tex]\[ x^2 - 14x + 49 = (x - 7)^2 \][/tex]

So, the factorized form is:
[tex]\[ (x - 7)^2 \][/tex]

### 19. [tex]\( -4x^2 - 24x - 36 \)[/tex]

This trinomial appears slightly different due to the negative sign and coefficients. We will factor out the common factor first, and then check if the remaining trinomial is a perfect square:

Given:
[tex]\[ -4x^2 - 24x - 36 \][/tex]

1. Factor out [tex]\(-4\)[/tex]:
[tex]\[ -4(x^2 + 6x + 9) \][/tex]

Now, we need to factorize the trinomial inside the parenthesis:
[tex]\[ x^2 + 6x + 9 \][/tex]

We previously recognized this form as:
[tex]\[ x^2 + 6x + 9 = (x + 3)^2 \][/tex]

So, putting it all together:
[tex]\[ -4(x^2 + 6x + 9) = -4(x + 3)^2 \][/tex]

Thus, the factorized form is:
[tex]\[ -4(x + 3)^2 \][/tex]

### Summary:

13. [tex]\( x^2 + 6x + 9 = (x + 3)^2 \)[/tex]

16. [tex]\( x^2 - 14x + 49 = (x - 7)^2 \)[/tex]

19. [tex]\( -4x^2 - 24x - 36 = -4(x + 3)^2 \)[/tex]