Find $ \left(3a-2b\right)^2 $ using formula.

$$ (A - B)^2 = \color{blue}{A^2} - 2 \cdot A \cdot B + \color{red}{B^2} $$

where $ A = \color{blue}{ 3a } $ and $ B = \color{red}{ 2b }$.

$$ \begin{aligned}\left(3a-2b\right)^2 = \color{blue}{\left( 3a \right)^2} -2 \cdot 3a \cdot 2b + \color{red}{\left( 2b \right)^2} = 9a^2-12ab+4b^2\end{aligned} $$

Find $ \left(3a+5b\right)^2 $ using formula.

$$ (A + B)^2 = \color{blue}{A^2} + 2 \cdot A \cdot B + \color{red}{B^2} $$

where $ A = \color{blue}{ 3a } $ and $ B = \color{red}{ 5b }$.

$$ \begin{aligned}\left(3a+5b\right)^2 = \color{blue}{\left( 3a \right)^2} +2 \cdot 3a \cdot 5b + \color{red}{\left( 5b \right)^2} = 9a^2+30ab+25b^2\end{aligned} $$

Multiply $ \color{blue}{2a} $ by $ \left( 9a^2-12ab+4b^2\right) $ $$ \color{blue}{2a} \cdot \left( 9a^2-12ab+4b^2\right) = 18a^3-24a^2b+8ab^2 $$Multiply $ \color{blue}{a} $ by $ \left( 9a^2+30ab+25b^2\right) $ $$ \color{blue}{a} \cdot \left( 9a^2+30ab+25b^2\right) = 9a^3+30a^2b+25ab^2 $$

Remove the parentheses by changing the sign of each term within them.

$$ - \left( 9a^3+30a^2b+25ab^2 \right) = -9a^3-30a^2b-25ab^2 $$

Combine like terms:

$$ \color{blue}{18a^3} \color{red}{-24a^2b} + \color{green}{8ab^2} \color{blue}{-9a^3} \color{red}{-30a^2b} \color{green}{-25ab^2} = \color{blue}{9a^3} \color{red}{-54a^2b} \color{green}{-17ab^2} $$