Answer:
[tex]\large\boxed{d=\sqrt{710}\approx26.65}\\\boxed{M(-4.5,\ -0.5,\ 0)}[/tex]
Step-by-step explanation:
[tex]\text{The formula of a length of the sebment:}\\\\d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2+(z_2-z_1)^2}\\\\\text{The formula of a midpoint:}\\\\M\left(\dfrac{x_1+x_2}{2},\ \dfrac{y_1+y_2}{2};\ \dfrac{z_1+z_2}{2}\right)[/tex]
[tex]\text{We have the endpoints of the segment:}\ (-7,\ -10,\ 9)\ \text{and}\ (-2,\ 9,\ -9).\\\\\text{Substitute}\\\\d=\sqrt{(-2-(-7))^2+(9-(-10))^2+(-9-9)^2}\\\\d=\sqrt{5^2+19^2+(-18)^2}\\\\d=\sqrt{25+361+324}\\\\d=\sqrt{710}\\\\M(x,\ y,\ z)\\\\x=\dfrac{(-7)+(-2)}{2}=\dfrac{-9}{2}=-4.5\\\\y=\dfrac{(-10)+9}{2}=\dfrac{-1}{2}=-0.5\\\\z=\dfrac{9+(-9)}{2}=\dfrac{0}{2}=0\\\\M(-4.5,\ -0.5,\ 0)[/tex]
