Straight Line Graphs 395F80
1. **Problem 1: Find the equation of a straight line**
Given two points $A(2,3)$ and $B(5,11)$, find the equation of the line passing through these points.
2. **Problem 2: Calculate the gradient and intercept**
Find the gradient and y-intercept of the line with equation $3x - 4y + 12 = 0$.
3. **Problem 3: Graph the line and find intercepts**
Graph the line $y = 2x - 3$ and find its x- and y-intercepts.
4. **Problem 4: Parallel and perpendicular lines**
Find the equation of a line parallel to $y = -\frac{1}{2}x + 4$ passing through $(6,1)$.
5. **Problem 5: Distance between a point and a line**
Find the distance from the point $(3,4)$ to the line $4x + 3y - 24 = 0$.
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**Solutions:**
1. Use formula for gradient $m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{11 - 3}{5 - 2} = \frac{8}{3}$.
Equation: $y - 3 = \frac{8}{3}(x - 2)$ simplifies to $y = \frac{8}{3}x - \frac{7}{3}$.
2. Rewrite $3x - 4y + 12 = 0$ as $y = \frac{3}{4}x + 3$.
Gradient $m = \frac{3}{4}$, y-intercept $c = 3$.
3. Intercepts:
- y-intercept: set $x=0$, $y = -3$.
- x-intercept: set $y=0$, $0 = 2x - 3 \Rightarrow x = \frac{3}{2}$.
Graph is a straight line crossing y-axis at -3 and x-axis at 1.5.
4. Parallel lines have same gradient $m = -\frac{1}{2}$.
Equation: $y - 1 = -\frac{1}{2}(x - 6)$, simplifies to $y = -\frac{1}{2}x + 4$.
5. Distance formula from point $(x_0,y_0)$ to line $Ax + By + C = 0$ is
$$d = \frac{|Ax_0 + By_0 + C|}{\sqrt{A^2 + B^2}} = \frac{|4(3) + 3(4) - 24|}{\sqrt{4^2 + 3^2}} = \frac{|12 + 12 - 24|}{5} = 0$$
The point lies on the line, so distance is 0.
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**Answers:**
1. $y = \frac{8}{3}x - \frac{7}{3}$
2. Gradient $\frac{3}{4}$, y-intercept 3
3. x-intercept $\frac{3}{2}$, y-intercept $-3$
4. $y = -\frac{1}{2}x + 4$
5. Distance = 0
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**Diagrams:**
- Problem 1: Line through points (2,3) and (5,11)
- Problem 3: Graph of $y=2x-3$ with intercepts
- Problem 4: Parallel line through (6,1)