1. **State the problem:**
We have the curve $C$ defined by the equation $$y = x^3 - 10x^2 + 27x - 23$$ and a point $P(5, -13)$ on $C$. We want to find the equation of the tangent line $l$ at $P$, verify where $l$ meets $C$ again, and find the area of the region $R$ bounded by $C$ and $l$.
2. **Find the slope of the tangent line $l$ at $P$ by differentiation:**
The derivative of $y$ with respect to $x$ is
$$\frac{dy}{dx} = 3x^2 - 20x + 27$$
Evaluate at $x=5$:
$$\frac{dy}{dx}\bigg|_{x=5} = 3(5)^2 - 20(5) + 27 = 75 - 100 + 27 = 2$$
So the slope $m$ of the tangent line at $P$ is $2$.
3. **Find the equation of the tangent line $l$:**
Using point-slope form:
$$y - y_1 = m(x - x_1)$$
where $(x_1, y_1) = (5, -13)$ and $m=2$:
$$y - (-13) = 2(x - 5)$$
$$y + 13 = 2x - 10$$
$$y = 2x - 23$$
So the equation of $l$ is $$y = 2x - 23$$.
4. **Verify that $l$ meets $C$ again on the y-axis:**
On the y-axis, $x=0$. Substitute into $l$:
$$y = 2(0) - 23 = -23$$
Substitute $x=0$ into $C$:
$$y = 0 - 0 + 0 - 23 = -23$$
Since both $C$ and $l$ have $y=-23$ at $x=0$, they meet again on the y-axis.
5. **Find the area of the region $R$ bounded by $C$ and $l$:**
The area is given by the integral of the difference between the curve and the line over the interval from $x=0$ to $x=5$:
$$\text{Area} = \int_0^5 \big[(x^3 - 10x^2 + 27x - 23) - (2x - 23)\big] \, dx$$
Simplify the integrand:
$$x^3 - 10x^2 + 27x - 23 - 2x + 23 = x^3 - 10x^2 + 25x$$
So,
$$\text{Area} = \int_0^5 (x^3 - 10x^2 + 25x) \, dx$$
Integrate term-by-term:
$$\int x^3 \, dx = \frac{x^4}{4}, \quad \int -10x^2 \, dx = -\frac{10x^3}{3}, \quad \int 25x \, dx = \frac{25x^2}{2}$$
Evaluate from 0 to 5:
$$\left[ \frac{x^4}{4} - \frac{10x^3}{3} + \frac{25x^2}{2} \right]_0^5 = \left( \frac{5^4}{4} - \frac{10 \times 5^3}{3} + \frac{25 \times 5^2}{2} \right) - 0$$
Calculate each term:
$$\frac{5^4}{4} = \frac{625}{4}$$
$$\frac{10 \times 5^3}{3} = \frac{10 \times 125}{3} = \frac{1250}{3}$$
$$\frac{25 \times 5^2}{2} = \frac{25 \times 25}{2} = \frac{625}{2}$$
Combine:
$$\text{Area} = \frac{625}{4} - \frac{1250}{3} + \frac{625}{2}$$
Find common denominator 12:
$$\frac{625}{4} = \frac{1875}{12}, \quad \frac{1250}{3} = \frac{5000}{12}, \quad \frac{625}{2} = \frac{3750}{12}$$
So,
$$\text{Area} = \frac{1875}{12} - \frac{5000}{12} + \frac{3750}{12} = \frac{1875 - 5000 + 3750}{12} = \frac{625}{12}$$
**Final answers:**
(a) Equation of tangent line $l$ is $$y = 2x - 23$$
(b) $l$ meets $C$ again on the y-axis at $(0, -23)$.
(c) The exact area of region $R$ is $$\frac{625}{12}$$.
Tangent Area 45Df4C
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