Responder
To graph the equation \( y = x^{2} - 2x - 8 \):
1. **Find the Roots**: Solve \( x^{2} - 2x - 8 = 0 \) to get \( x = 4 \) and \( x = -2 \). Plot points (4,0) and (-2,0).
2. **Find the Vertex**: Use \( x = -\frac{b}{2a} = 1 \). Substitute into the equation to find \( y = -9 \). Plot vertex at (1, -9).
3. **Find the y-intercept**: Set \( x = 0 \) to get \( y = -8 \). Plot point (0, -8).
4. **Graph the Parabola**: Draw a symmetric "U" shape with the vertex at (1, -9), passing through the roots and y-intercept.
Here's a rough sketch:
```
y
↑
5 |
4 |
3 |
2 |
1 |
0 —+————•————•————•————→ x
| (-2,0) (4,0)
-1 |
-2 |
-3 |
-4 |
-5 |
-6 |
-7 |
-8 | • (0,-8)
-9 | • (1,-9)
-10 |
|
+--------------------------------
-2 -1 0 1 2 3 4
```
The parabola opens upward, symmetric about the line \( x = 1 \).
Solución
We want to graph the quadratic
y = x² – 2x – 8.
Step 1. Find the Roots:
To find the x-intercepts, set y = 0:
x² – 2x – 8 = 0.
Factor the quadratic:
(x – 4)(x + 2) = 0.
So, the roots are:
x – 4 = 0 ⟹ x = 4,
x + 2 = 0 ⟹ x = –2.
These give the points (4, 0) and (–2, 0).
Step 2. Find the Vertex:
For a quadratic in the form y = ax² + bx + c, the x-coordinate of the vertex is given by
x = –b/(2a).
Here, a = 1 and b = –2:
x = –(–2)/(2·1) = 2/2 = 1.
Now substitute x = 1 into the equation to get y:
y = (1)² – 2(1) – 8 = 1 – 2 – 8 = –9.
Thus, the vertex is at (1, –9).
Step 3. Find the y-intercept:
Set x = 0:
y = 0² – 2·0 – 8 = –8.
So, the y-intercept is (0, –8).
Step 4. Graphing:
1. Plot the vertex at (1, –9). This is the lowest point on the parabola (since a > 0, the parabola opens upward).
2. Plot the roots (–2, 0) and (4, 0).
3. Plot the y-intercept (0, –8).
4. Draw a smooth curve through these points forming a “U” shape. The parabola is symmetric about the vertical line x = 1.
Here is a rough sketch of the graph:
y
↑
5 |
4 |
3 |
2 |
1 |
y=0 —+————•————•————•————→ x
| (–2,0) (4,0)
-1 |
-2 |
-3 |
-4 |
-5 |
-6 |
-7 |
-8 | • (0,–8)
-9 | • (1,–9)
-10 |
|
+--------------------------------
-2 -1 0 1 2 3 4
Remember, the parabola is symmetric about the vertical line line x = 1. You can plot additional points on both sides of the vertex if needed for accuracy.
That is the graph of y = x² – 2x – 8, complete with its roots (–2, 0) and (4, 0) and vertex (1, –9).
Respondido por UpStudy AI y revisado por un tutor profesional

Explicar

Simplifique esta solución