What is the equation of the quadratic function represented by this table?

[tex]\[
\begin{array}{|c|c|}
\hline
x & y \\
\hline
-3 & 3.75 \\
\hline
-2 & 4 \\
\hline
-1 & 3.75 \\
\hline
0 & 3 \\
\hline
1 & 1.75 \\
\hline
\end{array}
\][/tex]

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



Answer :

To find the equation of the quadratic function that fits the given table of values, we will start assuming the standard form of the quadratic function which is:

[tex]\[ y = a(x - b)^2 + c \][/tex]

We have the following points from the table:
1. [tex]\((-3, 3.75)\)[/tex]
2. [tex]\((-2, 4)\)[/tex]
3. [tex]\((-1, 3.75)\)[/tex]
4. [tex]\((0, 3)\)[/tex]
5. [tex]\((1, 1.75)\)[/tex]

We need to find the values of [tex]\(a\)[/tex], [tex]\(b\)[/tex], and [tex]\(c\)[/tex].

### Step 1: Identify the Vertex

From the table, notice that the y-values increase and then decrease, indicating a parabola which opens upwards or downwards. The vertex of the parabola occurs at the maximum or minimum point of the function.

From the table:
- At [tex]\(x = -2\)[/tex], [tex]\(y\)[/tex] is maximum (since it's not the maximum in the table but it's higher than its neighbors).

Thus, the vertex is at [tex]\((-2, 4)\)[/tex].
So, [tex]\(b = -2\)[/tex] and [tex]\(c = 4\)[/tex].

### Step 2: Substitute the Vertex Form

We now have part of the quadratic equation in the form:
[tex]\[ y = a(x - (-2))^2 + 4 \][/tex]
[tex]\[ y = a(x + 2)^2 + 4 \][/tex]

### Step 3: Use Another Point to Solve for [tex]\(a\)[/tex]

We can use any other point to find the value of [tex]\(a\)[/tex]. Let's use the point [tex]\((-3, 3.75)\)[/tex].

Substitute [tex]\((-3, 3.75)\)[/tex] into the equation:
[tex]\[ 3.75 = a(-3 + 2)^2 + 4 \][/tex]
[tex]\[ 3.75 = a(-1)^2 + 4 \][/tex]
[tex]\[ 3.75 = a(1) + 4 \][/tex]
[tex]\[ 3.75 = a + 4 \][/tex]

Solving for [tex]\(a\)[/tex]:
[tex]\[ a = 3.75 - 4 \][/tex]
[tex]\[ a = -0.25 \][/tex]

### Step 4: Verify using Another Point

We'll verify by using another point [tex]\((0, 3)\)[/tex]:
[tex]\[ y = -0.25(x + 2)^2 + 4 \][/tex]
Substitute [tex]\(x = 0\)[/tex]:
[tex]\[ 3 = -0.25(0 + 2)^2 + 4 \][/tex]
[tex]\[ 3 = -0.25(2)^2 + 4 \][/tex]
[tex]\[ 3 = -0.25(4) + 4 \][/tex]
[tex]\[ 3 = -1 + 4 \][/tex]
[tex]\[ 3 = 3 \][/tex]

The equation verifies correctly.

### Final Quadratic Equation

The quadratic function that represents the given table is:
[tex]\[ y = -0.25(x + 2)^2 + 4 \][/tex]

In the format [tex]\(y = a(x - b)^2 + c\)[/tex], the values are:
[tex]\[ a = -0.25 \][/tex]
[tex]\[ b = -2 \][/tex]
[tex]\[ c = 4 \][/tex]

So the complete quadratic equation is:
[tex]\[ y = -0.25(x + 2)^2 + 4 \][/tex]