Find $ \left(x+2\right)^2 $ using formula.

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

where $ A = \color{blue}{ x } $ and $ B = \color{red}{ 2 }$.

$$ \begin{aligned}\left(x+2\right)^2 = \color{blue}{x^2} +2 \cdot x \cdot 2 + \color{red}{2^2} = x^2+4x+4\end{aligned} $$

Multiply each term of $ \left( \color{blue}{x^2+4x+4}\right) $ by each term in $ \left( x-1\right) $.

$$ \left( \color{blue}{x^2+4x+4}\right) \cdot \left( x-1\right) = x^3-x^2+4x^2 -\cancel{4x}+ \cancel{4x}-4 $$

Combine like terms:

$$ x^3 \color{blue}{-x^2} + \color{blue}{4x^2} \, \color{red}{ -\cancel{4x}} \,+ \, \color{red}{ \cancel{4x}} \,-4 = x^3+ \color{blue}{3x^2} -4 $$

Multiply each term of $ \left( \color{blue}{x^3+3x^2-4}\right) $ by each term in $ \left( 3x+1\right) $.

$$ \left( \color{blue}{x^3+3x^2-4}\right) \cdot \left( 3x+1\right) = 3x^4+x^3+9x^3+3x^2-12x-4 $$

Combine like terms:

$$ 3x^4+ \color{blue}{x^3} + \color{blue}{9x^3} +3x^2-12x-4 = 3x^4+ \color{blue}{10x^3} +3x^2-12x-4 $$

Multiply each term of $ \left( \color{blue}{3x^4+10x^3+3x^2-12x-4}\right) $ by each term in $ \left( 2x+1\right) $.

$$ \left( \color{blue}{3x^4+10x^3+3x^2-12x-4}\right) \cdot \left( 2x+1\right) = 6x^5+3x^4+20x^4+10x^3+6x^3+3x^2-24x^2-12x-8x-4 $$

Combine like terms:

$$ 6x^5+ \color{blue}{3x^4} + \color{blue}{20x^4} + \color{red}{10x^3} + \color{red}{6x^3} + \color{green}{3x^2} \color{green}{-24x^2} \color{orange}{-12x} \color{orange}{-8x} -4 = \\ = 6x^5+ \color{blue}{23x^4} + \color{red}{16x^3} \color{green}{-21x^2} \color{orange}{-20x} -4 $$