F(3, 1), G(5, 2), H(2, 4), J(1, 6).
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
Part A)
FG:
[tex]slope\ m_{FG}=\dfrac{2-1}{5-3}=\dfrac{1}{2}[/tex]
Part B)
HJ:
[tex]slope\ m_{HJ}=\dfrac{6-4}{1-2}=\dfrac{2}{-1}=-2[/tex]
Part C)
[tex]\text{Let}\ k:y=m_1x+b_1\ \text{and}\ l:y=m_2x+b_2,\ \text{then}\\\\l\ \perp\ k\iff m_1m_2=-1\to m_2=-\dfrac{1}{m_1}\\\\l\ \parallel\ k\iff m_1=m_2[/tex]
We have
[tex]m_1=\dfrac{1}{2},\ m_2=-2\\\\m_1\neq m_2\\\\m_1m_2=\left(\dfrac{1}{2}\right)\left(-2\right)=-1[/tex]
Therefore the lines are perpendicular.