Multiply polynomial $ \, \color{blue}{ x-1 } \, $ by $ \, \color{orangered}{ x+5 }$.

$$ \left( \color{blue}{x-1} \right) \cdot \left( \color{orangered}{x+5} \right) = x^2+4x-5 $$

In this example we are multiplying two binomials so FOIL method can be used.

$$ \begin{aligned} \left( \color{blue}{ x-1}\right) \cdot \left( \color{orangered}{ x+5}\right) &= \underbrace{ \color{blue}{x} \cdot \color{orangered}{x} }_{\text{FIRST}} + \underbrace{ \color{blue}{x} \cdot \color{orangered}{5} }_{\text{OUTER}} + \underbrace{ \left( \color{blue}{-1} \right) \cdot \color{orangered}{x} }_{\text{INNER}} + \underbrace{ \left( \color{blue}{-1} \right) \cdot \color{orangered}{5} }_{\text{LAST}} = \\ &= x^2 + 5x + \left( -x\right) + \left( -5\right) = \\ &= x^2 + 5x + \left( -x\right) + \left( -5\right) = \\ &= x^2+4x-5; \end{aligned} $$

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