$d\left( {M;\left( P \right)} \right) = \dfrac{{\left| {a{x_0} + b{y_0} + c{z_0} + d} \right|}}{{\sqrt {{a^2} + {b^2} + {c^2}} }}$      

$d\left( {M;\left( P \right)} \right) = \dfrac{{a{x_0} + b{y_0} + c{z_0} + d}}{{\sqrt {{a^2} + {b^2} + {c^2}} }}$

$d\left( {M;\left( P \right)} \right) = \dfrac{{\left| {a{x_0} + b{y_0} + c{z_0} + d} \right|}}{{{a^2} + {b^2} + {c^2}}}$         

$d\left( {M;\left( P \right)} \right) = \dfrac{{a{x_0} + b{y_0} + c{z_0} + d}}{{{a^2} + {b^2} + {c^2}}}$