\[\boxed{\mathbf{678.}ОК\ ГДЗ\ –\ домашка\ на\ 5}\]
\[Формула:\]
\[\left( x - x_{0} \right)^{2} + \left( y - y_{0} \right)^{2} + \left( z - z_{0} \right)^{2} =\]
\[= R^{2}.\]
\[\textbf{а)}\ A(2; - 4;7);\ \ R = 3:\]
\[(x - 2)^{2} + (y + 4)^{2} + (z - 7)^{2} =\]
\[= 9.\]
\[\textbf{б)}\ A(0;0;0);\ \ R = \sqrt{2}:\]
\[x^{2} + y^{2} + z^{2} = 2.\]
\[\textbf{в)}\ A(2;0;0);\ \ R = 4:\]
\[(x - 2)^{2} + y^{2} + z^{2} = 16.\ \]