Question 4 of 10

The vertex of this parabola is at [tex](-5,4)[/tex]. Which of the following could be its equation?

A. [tex]y=-(x-5)^2+4[/tex]

B. [tex]y=-(x-5)^2-4[/tex]

C. [tex]y=-(x+5)^2+4[/tex]

D. [tex]y=-(x+5)^2-4[/tex]



Answer :

To determine which equation represents a parabola with its vertex at [tex]\((-5, 4)\)[/tex], we need to consider the vertex form of a quadratic equation. The vertex form is given by:

[tex]\[ y = a(x - h)^2 + k \][/tex]

where [tex]\((h, k)\)[/tex] is the vertex. For our problem, the vertex [tex]\((h, k)\)[/tex] is [tex]\((-5, 4)\)[/tex]. Therefore:

- [tex]\( h = -5 \)[/tex]
- [tex]\( k = 4 \)[/tex]

Substitute the vertex coordinates into the vertex form:

[tex]\[ y = a(x + 5)^2 + 4 \][/tex]

Here, [tex]\( (x - (-5)) \)[/tex] simplifies to [tex]\( (x + 5) \)[/tex]. The coefficient [tex]\( a \)[/tex] determines the direction and width of the parabola. Since the problem indicates that the parabola opens downwards, [tex]\( a \)[/tex] must be negative.

We now need to match this equation to one of the given options:

A. [tex]\( y = -(x - 5)^2 + 4 \)[/tex]
B. [tex]\( y = -(x - 5)^2 - 4 \)[/tex]
C. [tex]\( y = -(x + 5)^2 + 4 \)[/tex]
D. [tex]\( y = -(x + 5)^2 - 4 \)[/tex]

Among these options, option C reflects [tex]\( a < 0 \)[/tex], [tex]\( h = -5 \)[/tex], and [tex]\( k = 4 \)[/tex] correctly:

[tex]\[ y = -(x + 5)^2 + 4 \][/tex]

Thus, the equation that matches a parabola with vertex [tex]\((-5, 4)\)[/tex] is:

Answer: C. [tex]\( y = -(x + 5)^2 + 4 \)[/tex]