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Identify the vertex for the equation [tex]\( y = x^2 + 4x + 3 \)[/tex].

A. [tex]\( (2, -1) \)[/tex]

B. [tex]\( (-2, -1) \)[/tex]

C. [tex]\( (2, 15) \)[/tex]

D. [tex]\( (-2, 15) \)[/tex]


Sagot :

To identify the vertex of the quadratic equation [tex]\( y = x^2 + 4x + 3 \)[/tex], let's follow these steps:

1. Understand the standard form of a quadratic equation:
A quadratic equation is typically written in the form [tex]\( y = ax^2 + bx + c \)[/tex], where:
- [tex]\( a \)[/tex] is the coefficient of [tex]\( x^2 \)[/tex]
- [tex]\( b \)[/tex] is the coefficient of [tex]\( x \)[/tex]
- [tex]\( c \)[/tex] is the constant term

For the given equation [tex]\( y = x^2 + 4x + 3 \)[/tex]:
- [tex]\( a = 1 \)[/tex]
- [tex]\( b = 4 \)[/tex]
- [tex]\( c = 3 \)[/tex]

2. Identify the x-coordinate of the vertex:
The x-coordinate of the vertex can be found using the formula [tex]\( x = -\frac{b}{2a} \)[/tex].

Substitute the values of [tex]\( a \)[/tex] and [tex]\( b \)[/tex] into the formula:
[tex]\[ x = -\frac{4}{2 \cdot 1} = -\frac{4}{2} = -2 \][/tex]

3. Identify the y-coordinate of the vertex:
Once we have the x-coordinate, we substitute [tex]\( x = -2 \)[/tex] back into the original equation to find the y-coordinate.

Substitute [tex]\( x = -2 \)[/tex] into [tex]\( y = x^2 + 4x + 3 \)[/tex]:
[tex]\[ y = (-2)^2 + 4(-2) + 3 \][/tex]
Calculate each term:
[tex]\[ y = 4 - 8 + 3 = -1 \][/tex]

4. Determine the vertex:
With the x-coordinate as [tex]\(-2\)[/tex] and the y-coordinate as [tex]\(-1\)[/tex], the vertex of the quadratic equation [tex]\( y = x^2 + 4x + 3 \)[/tex] is:
[tex]\[ (-2, -1) \][/tex]

5. Identify the correct option:
Based on the options provided:
- [tex]\( \boxed{(-2, -1)} \)[/tex] is the correct answer.

So, the vertex of the equation [tex]\( y = x^2 + 4x + 3 \)[/tex] is [tex]\( (-2, -1) \)[/tex]. Therefore, the correct option is B.