$a ^ { 2 } - b ^ { 2 } - \left ( \color{#FF6800}{ a } \color{#FF6800}{ - } \color{#FF6800}{ b } \right ) ^ { \color{#FF6800}{ 2 } }$
$ $ Expand the binomial expression $ $
$a ^ { 2 } - b ^ { 2 } - \left ( \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ - } \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b } \color{#FF6800}{ + } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } \right )$
$a ^ { 2 } - b ^ { 2 } \color{#FF6800}{ - } \left ( \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ - } \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b } \color{#FF6800}{ + } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } \right )$
$ $ Change the symbol of each term in parentheses when there is a (-) symbol in front of parentheses $ $
$a ^ { 2 } - b ^ { 2 } \color{#FF6800}{ - } \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } + \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b } \color{#FF6800}{ - } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } }$
$\color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ - } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ - } \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ + } \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b } \color{#FF6800}{ - } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } }$
$ $ Organize the similar terms $ $
$\left ( \color{#FF6800}{ 1 } \color{#FF6800}{ - } \color{#FF6800}{ 1 } \right ) \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ + } \left ( \color{#FF6800}{ - } \color{#FF6800}{ 1 } \color{#FF6800}{ - } \color{#FF6800}{ 1 } \right ) \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ + } \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b }$
$\left ( \color{#FF6800}{ 1 } \color{#FF6800}{ - } \color{#FF6800}{ 1 } \right ) \color{#FF6800}{ a } ^ { \color{#FF6800}{ 2 } } + \left ( - 1 - 1 \right ) b ^ { 2 } + 2 a b$
$ $ Organize the mononomial expression $ $
$\color{#FF6800}{ 0 } + \left ( - 1 - 1 \right ) b ^ { 2 } + 2 a b$
$0 + \left ( \color{#FF6800}{ - } \color{#FF6800}{ 1 } \color{#FF6800}{ - } \color{#FF6800}{ 1 } \right ) \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } + 2 a b$
$ $ Arrange the constant term $ $
$0 \color{#FF6800}{ - } \color{#FF6800}{ 2 } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } + 2 a b$
$\color{#FF6800}{ 0 } - 2 b ^ { 2 } + 2 a b$
$ $ 0 does not change when you add or subtract $ $
$- 2 b ^ { 2 } + 2 a b$
$\color{#FF6800}{ - } \color{#FF6800}{ 2 } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } } \color{#FF6800}{ + } \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b }$
$ $ Sort the polynomial expressions in descending order $ $
$\color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ b } \color{#FF6800}{ - } \color{#FF6800}{ 2 } \color{#FF6800}{ b } ^ { \color{#FF6800}{ 2 } }$