Line Intersection F2Feed
1. **Problem 33:** A line from the point $(2,3)$ is perpendicular to the line $y=\frac{1}{3}x+1$. Find the coordinates of the intersection point $P$.
2. **Formula and rules:**
- The slope of the given line is $m=\frac{1}{3}$.
- The slope of a line perpendicular to it is the negative reciprocal: $m_\perp = -3$.
- Equation of the perpendicular line through $(2,3)$ is $y - 3 = -3(x - 2)$.
3. **Find the equation of the perpendicular line:**
$$y - 3 = -3x + 6 \implies y = -3x + 9$$
4. **Find intersection point $P$ by solving system:**
Given lines:
$$y = \frac{1}{3}x + 1$$
$$y = -3x + 9$$
Set equal:
$$\frac{1}{3}x + 1 = -3x + 9$$
Multiply both sides by 3:
$$x + 3 = -9x + 27$$
$$x + 9x = 27 - 3$$
$$10x = 24$$
$$x = \frac{24}{10} = 2.4$$
5. **Find $y$ coordinate:**
$$y = \frac{1}{3}(2.4) + 1 = 0.8 + 1 = 1.8$$
6. **Coordinates of $P$ are:**
$$(2.4, 1.8)$$
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7. **Problem 34(a):** Gradient of line $l$ with equation $y=5x+12$ is the coefficient of $x$.
8. **Answer:**
$$\text{Gradient} = 5$$
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9. **Problem 34(b):** Find where line $l$ crosses the x-axis.
10. At x-axis, $y=0$, so solve:
$$0 = 5x + 12$$
$$5x = -12$$
$$x = -\frac{12}{5} = -2.4$$
11. Coordinates of x-intercept:
$$(-2.4, 0)$$
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12. **Problem 34(c):** Find gradient $k$ of line perpendicular to $l$.
13. Since gradient of $l$ is $5$, perpendicular gradient is negative reciprocal:
$$k = -\frac{1}{5}$$
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**Final answers:**
- Problem 33: $P = (2.4, 1.8)$
- Problem 34(a): Gradient $= 5$
- Problem 34(b): x-intercept $= (-2.4, 0)$
- Problem 34(c): $k = -\frac{1}{5}$