Multiply polynomial $ \, \color{blue}{ x+6 } \, $ by $ \, \color{orangered}{ x+3 }$.

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

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

$$ \begin{aligned} \left( \color{blue}{ x+6}\right) \cdot \left( \color{orangered}{ x+3}\right) &= \underbrace{ \color{blue}{x} \cdot \color{orangered}{x} }_{\text{FIRST}} + \underbrace{ \color{blue}{x} \cdot \color{orangered}{3} }_{\text{OUTER}} + \underbrace{ \color{blue}{6} \cdot \color{orangered}{x} }_{\text{INNER}} + \underbrace{ \color{blue}{6} \cdot \color{orangered}{3} }_{\text{LAST}} = \\ &= x^2 + 3x + 6x + 18 = \\ &= x^2 + 3x + 6x + 18 = \\ &= x^2+9x+18; \end{aligned} $$

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