# What is the distance between (3, –1, 1)  and (3, 2, 1) ?

The distance D = $\sqrt{{\left({x}_{2} - {x}_{1}\right)}^{2} + {\left({y}_{2} - {y}_{1}\right)}^{2} + {\left({z}_{2} - {z}_{1}\right)}^{2}}$
So D = $\sqrt{{\left(3 - 3\right)}^{2} + {\left(2 + 1\right)}^{2} + {\left(1 - 1\right)}^{2}} \mathmr{and} D = \sqrt{9} \mathmr{and} D = 3 \left[A n s\right]$