Chapter 8.3, Problem 21P

Simplify each product using the FOIL method.

$(k-9)(k+5)$

To determine

To simplify: $(k-9)(k+5)$ using the FOIL method.

Answer to Problem 21P

  $k^2-4k-45$

Explanation of Solution

Given information: $(k-9)(k+5)$

Calculation:

  $\begin{array}{l}(k-9)(k+5)\\ =k\cdot k+k\cdot 5+(-9)\cdot k+(-9)\cdot 5\\ =k^2+5k-9k-45\\ =k^2-4k-45\end{array}$

Thus, $(k-9)(k+5)=k^2-4k-45$