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Factor completely [tex][tex]$9x^2 - 25$[/tex][/tex].

A. [tex][tex]$(3x + 5)(3x - 5)$[/tex][/tex]

B. [tex][tex]$(3x - 5)(3x - 5)$[/tex][/tex]

C. [tex][tex]$(9x + 5)(x - 5)$[/tex][/tex]

D. [tex][tex]$(9x - 5)(x + 5)$[/tex][/tex]


Sagot :

To factor the given quadratic expression [tex]\( 9x^2 - 25 \)[/tex] completely, we will follow a step-by-step approach:

1. Recognize the form of the expression: Notice that the given expression, [tex]\( 9x^2 - 25 \)[/tex], is a difference of squares. The difference of squares can be factored using the identity:
[tex]\[ a^2 - b^2 = (a - b)(a + b) \][/tex]

2. Identify [tex]\(a\)[/tex] and [tex]\(b\)[/tex] in the expression [tex]\( 9x^2 - 25 \)[/tex]:
- In our case, [tex]\( 9x^2 \)[/tex] is a perfect square, and so is [tex]\( 25 \)[/tex].
- We can write [tex]\( 9x^2 \)[/tex] as [tex]\( (3x)^2 \)[/tex] and [tex]\( 25 \)[/tex] as [tex]\( 5^2 \)[/tex].

3. Apply the difference of squares identity:
Given:
[tex]\[ 9x^2 - 25 \][/tex]
Write it as:
[tex]\[ (3x)^2 - 5^2 \][/tex]
Now, apply the difference of squares formula:
[tex]\[ (3x)^2 - 5^2 = (3x - 5)(3x + 5) \][/tex]

4. Verify the factors given in the multiple-choice options:
- Option 1: [tex]\( (3x + 5)(3x - 5) \)[/tex]
- Option 2: [tex]\( (3x - 5)(3x - 5) \)[/tex]
- Option 3: [tex]\( (9x + 5)(x - 5) \)[/tex]
- Option 4: [tex]\( (9x - 5)(x + 5) \)[/tex]

Comparing these with our factorization [tex]\( (3x - 5)(3x + 5) \)[/tex], we see that the correct factorization corresponds to Option 1:

Thus, the completely factored form of [tex]\( 9x^2 - 25 \)[/tex] is:
[tex]\[ (3x - 5)(3x + 5) \][/tex]