1. **Stating the problem:** We are given functions $f(x)$ and points $P(x_0, y_0)$, and we need to find the equations of the tangent lines to the graph of $f$ that pass through $P$. We also find the points of contact on the graph.
2. **Formula and rules:** The tangent line to $f$ at point $x=a$ has slope $f'(a)$ and equation:
$$y = f'(a)(x - a) + f(a)$$
We want this line to pass through $P(x_0, y_0)$, so:
$$y_0 = f'(a)(x_0 - a) + f(a)$$
This gives an equation in $a$ to solve for the point of contact.
3. **Apply to problem (a):**
- $f(x) = -x^2 + 5$
- $P(0, 9)$
Calculate derivative:
$$f'(x) = -2x$$
Equation of tangent at $x=a$:
$$y = -2a(x - a) + (-a^2 + 5) = -2a x + 2a^2 - a^2 + 5 = -2a x + a^2 + 5$$
Since tangent passes through $P(0,9)$:
$$9 = -2a \cdot 0 + a^2 + 5$$
$$9 = a^2 + 5$$
$$a^2 = 4$$
$$a = \pm 2$$
Points of contact:
- For $a=2$: $f(2) = -4 + 5 = 1$
- For $a=-2$: $f(-2) = -4 + 5 = 1$
Tangent lines:
- For $a=2$:
$$y = -2 \cdot 2 (x - 2) + f(2) = -4(x - 2) + 1 = -4x + 8 + 1 = -4x + 9$$
- For $a=-2$:
$$y = -2 \cdot (-2)(x + 2) + f(-2) = 4(x + 2) + 1 = 4x + 8 + 1 = 4x + 9$$
**Answer (a):** Tangent lines are $y = -4x + 9$ and $y = 4x + 9$ with points of contact $(2,1)$ and $(-2,1)$.
4. **Summary:** We found the tangent lines passing through $P$ by solving for $a$ in the tangent line equation and then writing the tangent line equations.
Since the user asked multiple parts but per instructions we solve only the first problem completely.
Tangent Lines 4Ba8Da
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