Select the correct answer.

Which equation models the same quadratic relationship as function [tex]\( f(x) = x^2 + 12x + 4 \)[/tex]?

A. [tex]\( y = (x + 6)^2 + 40 \)[/tex]

B. [tex]\( y = (x + 6)^2 - 32 \)[/tex]

C. [tex]\( y = (x \cdot 6)^2 - 32 \)[/tex]

D. [tex]\( y = (x - 6)^2 + 40 \)[/tex]



Answer :

To determine which equation models the same quadratic relationship as the given function [tex]\( f(x) = x^2 + 12x + 4 \)[/tex], we need to check if the given function can be rewritten in the form of the options presented. Let's start by rewriting [tex]\( f(x) \)[/tex] in a form that resembles the given choices.

1. Complete the square for [tex]\( f(x) = x^2 + 12x + 4 \)[/tex]:

The standard form of completing the square for a quadratic function [tex]\( ax^2 + bx + c \)[/tex] involves creating an expression that represents a perfect square trinomial. Here's the process:

[tex]\[ f(x) = x^2 + 12x + 4 \][/tex]

First, take the coefficient of [tex]\( x \)[/tex], which is 12, and divide it by 2:

[tex]\[ \frac{12}{2} = 6 \][/tex]

Next, square this result:

[tex]\[ 6^2 = 36 \][/tex]

Add and subtract this square inside the function:

[tex]\[ f(x) = x^2 + 12x + 36 - 36 + 4 \][/tex]

Group the perfect square trinomial and simplify the constant term:

[tex]\[ f(x) = (x + 6)^2 - 36 + 4 \][/tex]

Simplify the constants:

[tex]\[ f(x) = (x + 6)^2 - 32 \][/tex]

2. Compare with the given options:

We can see that the equivalent form of [tex]\( x^2 + 12x + 4 \)[/tex] after completing the square is:

[tex]\[ f(x) = (x + 6)^2 - 32 \][/tex]

Now, we'll match this with the given options:

- Option A: [tex]\( y = (x + 6)^2 + 40 \)[/tex]

This is incorrect because it has +40 instead of -32.

- Option B: [tex]\( y = (x + 6)^2 - 32 \)[/tex]

This is correct because it matches our derived form exactly.

- Option C: [tex]\( y = (x \cdot 6)^2 - 32 \)[/tex]

This is incorrect because it involves [tex]\( x \cdot 6 \)[/tex] instead of [tex]\( x + 6 \)[/tex].

- Option D: [tex]\( y = (x - 6)^2 + 40 \)[/tex]

This is incorrect because it involves [tex]\( x - 6 \)[/tex] instead of [tex]\( x + 6 \)[/tex], and +40 instead of -32.

Therefore, the correct answer is:

[tex]\[ \boxed{B} \][/tex]