Multiply each term of $ \left( \color{blue}{x+15}\right) $ by each term in $ \left( x+10\right) $.

$$ \left( \color{blue}{x+15}\right) \cdot \left( x+10\right) = x^2+10x+15x+150 $$

Combine like terms:

$$ x^2+ \color{blue}{10x} + \color{blue}{15x} +150 = x^2+ \color{blue}{25x} +150 $$

Multiply each term of $ \left( \color{blue}{x^2+25x+150}\right) $ by each term in $ \left( x+10\right) $.

$$ \left( \color{blue}{x^2+25x+150}\right) \cdot \left( x+10\right) = x^3+10x^2+25x^2+250x+150x+1500 $$

Combine like terms:

$$ x^3+ \color{blue}{10x^2} + \color{blue}{25x^2} + \color{red}{250x} + \color{red}{150x} +1500 = x^3+ \color{blue}{35x^2} + \color{red}{400x} +1500 $$

Multiply each term of $ \left( \color{blue}{x^3+35x^2+400x+1500}\right) $ by each term in $ \left( x-1\right) $.

$$ \left( \color{blue}{x^3+35x^2+400x+1500}\right) \cdot \left( x-1\right) = x^4-x^3+35x^3-35x^2+400x^2-400x+1500x-1500 $$

Combine like terms:

$$ x^4 \color{blue}{-x^3} + \color{blue}{35x^3} \color{red}{-35x^2} + \color{red}{400x^2} \color{green}{-400x} + \color{green}{1500x} -1500 = \\ = x^4+ \color{blue}{34x^3} + \color{red}{365x^2} + \color{green}{1100x} -1500 $$

Multiply each term of $ \left( \color{blue}{x^4+34x^3+365x^2+1100x-1500}\right) $ by each term in $ \left( x-14\right) $.

$$ \left( \color{blue}{x^4+34x^3+365x^2+1100x-1500}\right) \cdot \left( x-14\right) = \\ = x^5-14x^4+34x^4-476x^3+365x^3-5110x^2+1100x^2-15400x-1500x+21000 $$

Combine like terms:

$$ x^5 \color{blue}{-14x^4} + \color{blue}{34x^4} \color{red}{-476x^3} + \color{red}{365x^3} \color{green}{-5110x^2} + \color{green}{1100x^2} \color{orange}{-15400x} \color{orange}{-1500x} +21000 = \\ = x^5+ \color{blue}{20x^4} \color{red}{-111x^3} \color{green}{-4010x^2} \color{orange}{-16900x} +21000 $$

Multiply $ \color{blue}{0} $ by $ \left( x^5+20x^4-111x^3-4010x^2-16900x+21000\right) $ $$ \color{blue}{0} \cdot \left( x^5+20x^4-111x^3-4010x^2-16900x+21000\right) = 0x^50x^40x^30x^20x0 $$

Combine like terms:

$$ 0 = 0 $$