How do you multiply (2r^2+7s^2)(2r^2-7s^2)?

Aug 14, 2016

Answer:

$4 {r}^{4} - 49 {s}^{4}$

Explanation:

We could use the usual method of binomial times binomial, but we should notice that this is the answer to the difference of squares.

$\left(x + y\right) \left(x - y\right) = {x}^{2} - {y}^{2}$

Therefore in this case:

$\left(2 {r}^{2} + 7 {s}^{2}\right) \left(2 {r}^{2} - 7 {s}^{2}\right) = 4 {r}^{4} - 49 {s}^{4}$