(n-6m)(6m+n) = n(6m+n) - 6m(6m+n)(n-6m)(6m+n) = 6mn + n^2 - 36m^2 - 6mn(n-6m)(6m+n) = n^2 - 36m^2(n-6m)(6m+n) = n^2 - 36m^2
(n-6m)(6m+n) = n(6m+n) - 6m(6m+n)
(n-6m)(6m+n) = 6mn + n^2 - 36m^2 - 6mn
(n-6m)(6m+n) = n^2 - 36m^2
(n-6m)(6m+n) = n^2 - 36m^2