Multiply $ \color{blue}{3} $ by $ \left( -x+1\right) $ $$ \color{blue}{3} \cdot \left( -x+1\right) = -3x+3 $$

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

$$ \left( \color{blue}{-3x+3}\right) \cdot \left( -x+2\right) = 3x^2-6x-3x+6 $$

Combine like terms:

$$ 3x^2 \color{blue}{-6x} \color{blue}{-3x} +6 = 3x^2 \color{blue}{-9x} +6 $$

Multiply each term of $ \left( \color{blue}{3x^2-9x+6}\right) $ by each term in $ \left( -x+3\right) $.

$$ \left( \color{blue}{3x^2-9x+6}\right) \cdot \left( -x+3\right) = -3x^3+9x^2+9x^2-27x-6x+18 $$

Combine like terms:

$$ -3x^3+ \color{blue}{9x^2} + \color{blue}{9x^2} \color{red}{-27x} \color{red}{-6x} +18 = -3x^3+ \color{blue}{18x^2} \color{red}{-33x} +18 $$

Multiply each term of $ \left( \color{blue}{-3x^3+18x^2-33x+18}\right) $ by each term in $ \left( -x+4\right) $.

$$ \left( \color{blue}{-3x^3+18x^2-33x+18}\right) \cdot \left( -x+4\right) = 3x^4-12x^3-18x^3+72x^2+33x^2-132x-18x+72 $$

Combine like terms:

$$ 3x^4 \color{blue}{-12x^3} \color{blue}{-18x^3} + \color{red}{72x^2} + \color{red}{33x^2} \color{green}{-132x} \color{green}{-18x} +72 = \\ = 3x^4 \color{blue}{-30x^3} + \color{red}{105x^2} \color{green}{-150x} +72 $$

Multiply each term of $ \left( \color{blue}{3x^4-30x^3+105x^2-150x+72}\right) $ by each term in $ \left( -x+5\right) $.

$$ \left( \color{blue}{3x^4-30x^3+105x^2-150x+72}\right) \cdot \left( -x+5\right) = \\ = -3x^5+15x^4+30x^4-150x^3-105x^3+525x^2+150x^2-750x-72x+360 $$

Combine like terms:

$$ -3x^5+ \color{blue}{15x^4} + \color{blue}{30x^4} \color{red}{-150x^3} \color{red}{-105x^3} + \color{green}{525x^2} + \color{green}{150x^2} \color{orange}{-750x} \color{orange}{-72x} +360 = \\ = -3x^5+ \color{blue}{45x^4} \color{red}{-255x^3} + \color{green}{675x^2} \color{orange}{-822x} +360 $$