1. **State the problem:** Given points $(-4,16)$, $(4,16)$, $(-5,25)$, and $(5,25)$, find the function that fits these points.
2. **Analyze the points:** Notice the points are symmetric about the y-axis, suggesting an even function, likely a quadratic or higher even power.
3. **Assume a quadratic function:** Let $y = ax^2 + bx + c$. Since the points are symmetric, $b=0$ (no linear term).
4. **Use points to find $a$ and $c$:**
- Using $(4,16)$: $16 = a(4)^2 + c = 16a + c$
- Using $(5,25)$: $25 = a(5)^2 + c = 25a + c$
5. **Solve the system:**
$$\begin{cases} 16 = 16a + c \\ 25 = 25a + c \end{cases}$$
Subtract first from second:
$$25 - 16 = 25a - 16a + c - c \Rightarrow 9 = 9a \Rightarrow a = 1$$
6. **Find $c$:**
$$16 = 16(1) + c \Rightarrow c = 0$$
7. **Final function:**
$$y = x^2$$
8. **Verify:**
- $(-4)^2 = 16$, $(4)^2 = 16$
- $(-5)^2 = 25$, $(5)^2 = 25$
All points satisfy $y = x^2$.
**Answer:** The function is $y = x^2$.
Quadratic Fit A1761B
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