1. **State the problem:**
We are given the function $y = x(x-4) - 5$ and asked to draw its graph for $-3 \leq x \leq 4$.
Then, we need to use this graph to answer two quadratic equations:
(a) $x^2 - 5x - 3 = 0$
(b) $x^2 - 3x + 4 = 0$
2. **Rewrite the function:**
Expand $y = x(x-4) - 5$:
$$y = x^2 - 4x - 5$$
3. **Graph features:**
This is a quadratic function with:
- $a = 1$, $b = -4$, $c = -5$
- Vertex at $x = -\frac{b}{2a} = -\frac{-4}{2 \times 1} = 2$
- Vertex $y$ value: $y = 2^2 - 4 \times 2 - 5 = 4 - 8 - 5 = -9$
- The parabola opens upwards since $a > 0$.
4. **Use the graph to solve the equations:**
The graph of $y = x^2 - 4x - 5$ is close to the equations given but not exactly the same. However, we can compare the roots of the given equations to the graph of $y = x^2 - 4x - 5$ to understand their solutions.
5. **Solve (a) $x^2 - 5x - 3 = 0$ algebraically:**
Use quadratic formula:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{5 \pm \sqrt{25 + 12}}{2} = \frac{5 \pm \sqrt{37}}{2}$$
Approximate roots:
$$x \approx \frac{5 \pm 6.08}{2}$$
So,
$$x_1 \approx \frac{5 + 6.08}{2} = 5.54$$
$$x_2 \approx \frac{5 - 6.08}{2} = -0.54$$
6. **Solve (b) $x^2 - 3x + 4 = 0$ algebraically:**
Discriminant:
$$\Delta = (-3)^2 - 4 \times 1 \times 4 = 9 - 16 = -7 < 0$$
Since discriminant is negative, no real roots.
7. **Summary:**
- Equation (a) has two real roots approximately $-0.54$ and $5.54$.
- Equation (b) has no real roots.
Since the graph of $y = x^2 - 4x - 5$ is similar but shifted compared to the equations, the roots differ slightly.
Quadratic Graph D21C2F
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