Answer
\[\left( x+9 \right)\left( x-5 \right)={{x}^{2}}+4x-45\]
Work Step by Step
Consider,
\[\begin{align}
& \left( x+9 \right)\left( x-5 \right)=\underbrace{x\cdot x}_{\text{F}}+\underbrace{x\cdot \left( -5 \right)}_{\text{O}}+\underbrace{9\cdot x}_{\text{I}}+\underbrace{9\cdot \left( -5 \right)}_{\text{L}} \\
& ={{x}^{2}}-5x+9x-45 \\
& ={{x}^{2}}+4x-45
\end{align}\]
where, “F” stands for the product of the first term, “O” stands for the product of the outside terms, “I” stands for the product of the inside term, and “L” stands for the product of the last term.
