Chapter 8.3, Problem 21PPS

To determine

To find: The product $\left(5r+7\right)\left(5r-7\right)$

Answer to Problem 21PPS

  $25r^2-49$

Explanation of Solution

Given:

  $\left(5r+7\right)\left(5r-7\right)$

Calculation:

Use FOIL method to multiply these binomials.

FOIL stands for “First, Outer, Inner, Last”. So, multiply the first terms of both binomials then outer, then inner and then last terms.

Using this method to multiply and then combine the like terms

  $\begin{array}{l}\left(5r+7\right)\left(5r-7\right)\\ =25r^2-35r+35r-49\\ =25r^2-49\end{array}$

So, the product of the binomial is $25r^2-49$