1. **State the problem:**
We have line $l$ with equation $2x - 3y = 12$.
Point $A$ is where $l$ cuts the x-axis.
Point $B$ is given as $(0, -4)$ on the y-axis.
We need to find:
(a) Coordinates of $A$.
(b) Slope of line $l$.
(c) Slope and equation of line $k$ perpendicular to $l$ passing through $B$.
(d) Coordinates of $C$, where $k$ crosses the x-axis.
(e) Area of triangle $ABC$.
2. **Find coordinates of $A$ (x-intercept of $l$):**
At the x-axis, $y=0$.
Substitute $y=0$ into $2x - 3y = 12$:
$$2x - 3(0) = 12 \implies 2x = 12$$
Divide both sides by 2:
$$\cancel{2}x = \frac{12}{\cancel{2}} \implies x = 6$$
So, $A = (6, 0)$.
3. **Find slope of line $l$:**
Rewrite $2x - 3y = 12$ in slope-intercept form $y = mx + c$:
$$2x - 3y = 12 \implies -3y = -2x + 12$$
Divide both sides by $-3$:
$$\cancel{-3}y = \frac{-2x + 12}{\cancel{-3}} \implies y = \frac{2}{3}x - 4$$
Slope $m_l = \frac{2}{3}$.
4. **Find slope and equation of line $k$ perpendicular to $l$ passing through $B(0, -4)$:**
Slope of $k$ is negative reciprocal of $m_l$:
$$m_k = -\frac{1}{m_l} = -\frac{1}{\frac{2}{3}} = -\frac{3}{2}$$
Equation of $k$ using point-slope form:
$$y - y_1 = m_k(x - x_1)$$
Substitute $B(0, -4)$:
$$y - (-4) = -\frac{3}{2}(x - 0) \implies y + 4 = -\frac{3}{2}x$$
Simplify:
$$y = -\frac{3}{2}x - 4$$
5. **Find coordinates of $C$ (x-intercept of $k$):**
At x-axis, $y=0$.
Substitute $y=0$ into $y = -\frac{3}{2}x - 4$:
$$0 = -\frac{3}{2}x - 4$$
Add 4 to both sides:
$$4 = -\frac{3}{2}x$$
Divide both sides by $-\frac{3}{2}$:
$$x = \frac{4}{-\frac{3}{2}} = 4 \times -\frac{2}{3} = -\frac{8}{3}$$
So, $C = \left(-\frac{8}{3}, 0\right)$.
6. **Find area of triangle $ABC$:**
Points are $A(6,0)$, $B(0,-4)$, $C\left(-\frac{8}{3},0\right)$.
Base $AC$ lies on x-axis, length:
$$AC = 6 - \left(-\frac{8}{3}\right) = 6 + \frac{8}{3} = \frac{18}{3} + \frac{8}{3} = \frac{26}{3}$$
Height is vertical distance from $B$ to x-axis:
$$|y_B| = |-4| = 4$$
Area formula:
$$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times \frac{26}{3} \times 4 = \frac{1}{2} \times \frac{104}{3} = \frac{104}{6} = \frac{52}{3}$$
**Final answers:**
(a) $A = (6, 0)$
(b) Slope of $l$ is $\frac{2}{3}$
(c) Slope of $k$ is $-\frac{3}{2}$ and equation is $y = -\frac{3}{2}x - 4$
(d) $C = \left(-\frac{8}{3}, 0\right)$
(e) Area of triangle $ABC$ is $\frac{52}{3}$ square units.
Line Intercepts E6988B
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