Parallelogram Pt
1. **State the problem:** We have a parallelogram PARM with points P(2,9), R(n,-13), T(10,-3), and M the midpoint of PT. We need to find:
3.1.1 The length of PT in surd form.
3.1.2 The gradient of PT.
3.1.3 The gradient of AR.
3.1.4 The coordinates of M.
3.2 The equation of PM in the form $y=mx+c$.
2. **Given:**
- $P=(2,9)$
- $T=(10,-3)$
- $M$ is midpoint of $PT$
- $PT \perp RT$
- $R=(n,-13)$
3. **Find length of PT:**
Length formula: $$\text{Length} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$$
Calculate:
$$PT = \sqrt{(10 - 2)^2 + (-3 - 9)^2} = \sqrt{8^2 + (-12)^2} = \sqrt{64 + 144} = \sqrt{208}$$
Simplify $\sqrt{208}$:
$$208 = 16 \times 13 \Rightarrow \sqrt{208} = \sqrt{16 \times 13} = 4\sqrt{13}$$
So, length of $PT = 4\sqrt{13}$.
4. **Find gradient of PT:**
Gradient formula:
$$m = \frac{y_2 - y_1}{x_2 - x_1}$$
Calculate:
$$m_{PT} = \frac{-3 - 9}{10 - 2} = \frac{-12}{8} = -\frac{3}{2}$$
5. **Find gradient of AR:**
Since $PARM$ is a parallelogram, $AR$ is parallel to $PM$.
First, find $M$ (midpoint of $PT$):
$$M_x = \frac{2 + 10}{2} = 6, \quad M_y = \frac{9 + (-3)}{2} = 3$$
So, $M = (6,3)$.
Gradient of $PM$:
$$m_{PM} = \frac{3 - 9}{6 - 2} = \frac{-6}{4} = -\frac{3}{2}$$
Since $AR \parallel PM$,
$$m_{AR} = -\frac{3}{2}$$
6. **Find coordinates of M:**
Already found:
$$M = (6,3)$$
7. **Find equation of PM:**
Use point-slope form:
$$y - y_1 = m(x - x_1)$$
Using point $P(2,9)$ and slope $m = -\frac{3}{2}$:
$$y - 9 = -\frac{3}{2}(x - 2)$$
Simplify:
$$y - 9 = -\frac{3}{2}x + 3$$
$$y = -\frac{3}{2}x + 3 + 9$$
$$y = -\frac{3}{2}x + 12$$
**Final answers:**
- Length of $PT = 4\sqrt{13}$
- Gradient of $PT = -\frac{3}{2}$
- Gradient of $AR = -\frac{3}{2}$
- Coordinates of $M = (6,3)$
- Equation of $PM: y = -\frac{3}{2}x + 12$