$- \sqrt{ \color{#FF6800}{ 125 } } + \dfrac { 15 } { \sqrt{ 5 } } - 2 \sqrt{ 45 }$
$ $ Organize the part that can be taken out of the radical sign inside the square root symbol $ $
$- \left ( \color{#FF6800}{ 5 } \sqrt{ \color{#FF6800}{ 5 } } \right ) + \dfrac { 15 } { \sqrt{ 5 } } - 2 \sqrt{ 45 }$
$\color{#FF6800}{ - } \left ( \color{#FF6800}{ 5 } \sqrt{ \color{#FF6800}{ 5 } } \right ) + \dfrac { 15 } { \sqrt{ 5 } } - 2 \sqrt{ 45 }$
$ $ Get rid of unnecessary parentheses $ $
$\color{#FF6800}{ - } \color{#FF6800}{ 5 } \sqrt{ \color{#FF6800}{ 5 } } + \dfrac { 15 } { \sqrt{ 5 } } - 2 \sqrt{ 45 }$
$- 5 \sqrt{ 5 } + \color{#FF6800}{ \dfrac { \color{#FF6800}{ 15 } } { \sqrt{ \color{#FF6800}{ 5 } } } } - 2 \sqrt{ 45 }$
$ $ Calculate the expression $ $
$- 5 \sqrt{ 5 } + \color{#FF6800}{ 3 } \sqrt{ \color{#FF6800}{ 5 } } - 2 \sqrt{ 45 }$
$- 5 \sqrt{ 5 } + 3 \sqrt{ 5 } \color{#FF6800}{ - } \color{#FF6800}{ 2 } \sqrt{ \color{#FF6800}{ 45 } }$
$ $ Simplify the expression $ $
$- 5 \sqrt{ 5 } + 3 \sqrt{ 5 } \color{#FF6800}{ - } \color{#FF6800}{ 6 } \sqrt{ \color{#FF6800}{ 5 } }$
$\color{#FF6800}{ - } \color{#FF6800}{ 5 } \sqrt{ \color{#FF6800}{ 5 } } \color{#FF6800}{ + } \color{#FF6800}{ 3 } \sqrt{ \color{#FF6800}{ 5 } } \color{#FF6800}{ - } \color{#FF6800}{ 6 } \sqrt{ \color{#FF6800}{ 5 } }$
$ $ Calculate between similar terms $ $
$\color{#FF6800}{ - } \color{#FF6800}{ 8 } \sqrt{ \color{#FF6800}{ 5 } }$