1) (m+n)(m-n) = m^2 - mn + mn - n^2 = m^2 - n^22) (c-d)(d+c) = cd + c^2 - cd - d^2 = c^2 - d^23) (x+y)(y-x) = xy - x^2 + y^2 - xy = y^2 - x^24) (x+2)(2-x) = 2x - x^2 + 4 - 2x = 4 - x^25) (n-2m)(n+2m) = n^2 + 2mn - 2mn - 4m^2 = n^2 - 4m^26) (8a+9b)(9b-8a) = 72ab - 64a^2 + 81b^2 - 72ab = 81b^2 - 64a^2
1) (m+n)(m-n) = m^2 - mn + mn - n^2 = m^2 - n^2
2) (c-d)(d+c) = cd + c^2 - cd - d^2 = c^2 - d^2
3) (x+y)(y-x) = xy - x^2 + y^2 - xy = y^2 - x^2
4) (x+2)(2-x) = 2x - x^2 + 4 - 2x = 4 - x^2
5) (n-2m)(n+2m) = n^2 + 2mn - 2mn - 4m^2 = n^2 - 4m^2
6) (8a+9b)(9b-8a) = 72ab - 64a^2 + 81b^2 - 72ab = 81b^2 - 64a^2