Question

select a suitable identity and find the following products
$(kl-mn)(kl+mn)$

Answer 1

$(kl-mn)(kl+mn)$

Using identity: $(a-b)(a+b)=a^2-b^2$

Therefore,

$(kl-mn)(kl+mn)$

$={\left(kl\right)}^2-{\left(mn\right)}^2$

$=k^2{l}^2-m^2{n}^2$