\[1)\ 6\ и\ 8i:\]
\[l = \sqrt{(6 - 0)^{2} + (0 - 8)^{2}} =\]
\[= \sqrt{6^{2} + 8^{2}} = \sqrt{36 + 64} =\]
\[= \sqrt{100} = 10.\]
\[2)\ 7i\ и - 2i:\]
\[l = \sqrt{(0 - 0)^{2} + (7 + 2)^{2}} =\]
\[= \sqrt{0^{2} + 9^{2}} = \sqrt{0 + 81} =\]
\[= \sqrt{81} = 9.\]
\[3)\ 1 + i\ и\ 2 + 3i:\]
\[l = \sqrt{(1 - 2)^{2} + (1 - 3)^{2}} =\]
\[= \sqrt{1^{2} + 2^{2}} = \sqrt{1 + 4} = \sqrt{5}.\]
\[4)\ 3 - 2i\ и\ 1 - 4i:\]
\[l = \sqrt{(3 - 1)^{2} + ( - 2 + 4)^{2}} =\]
\[= \sqrt{2^{2} + 2^{2}} = \sqrt{4 + 4} = \sqrt{8} =\]
\[= \sqrt{4 \bullet 2} = 2\sqrt{2}.\]