Let the given points be A(4, 7, 8), B(2, 3, 4), C(–1, –2, 1), D(1, 2, 5)Direction ratios of AB are < 2 –4, 3 – 7, 4 – 8 > or <–2, –4, –4> and direction ratios of CD are <1 + 1, 2 + 2, 5 – 1 > or <2, 4, 4>Two lines with direction ratios $a_1, b_1, c_1$ and $a_2, b_2, c_2$ are parallel if $\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}$ $\Rightarrow -\frac{2}{2} = -\frac{4}{4} = -\frac{4}{4}$$\Rightarrow AB \parallel CD$