# How do you find the product (7z^2+5y^2)(7z^2-5y^2)?

Jan 15, 2017

$49 {z}^{4} - 25 {y}^{4}$

#### Explanation:

$\left(a + b\right) \left(a - b\right) = {a}^{2} - {b}^{2}$

In this case, $a = 7 {z}^{2}$ and $b = 5 {y}^{2}$

${a}^{2} = {7}^{2} \cdot {\left({z}^{2}\right)}^{2} = 49 {z}^{4}$

${b}^{2} = {5}^{2} \cdot {\left({y}^{2}\right)}^{2} = 25 {y}^{4}$

${a}^{2} - {b}^{2} = 49 {z}^{4} - 25 {y}^{4}$