1) (a-b)(a+b) = a^2 - ab + ab - b^2 = a^2 - b^2(a-b)(a-b) = a^2 - ab - ab + b^2 = a^2 - 2ab + b^2(a+b)(a+b) = a^2 + ab + ab + b^2 = a^2 + 2ab + b^2
2) (m-n)(m+n) = m^2 - mn + mn - n^2 = m^2 - n^2(m+n)(m+n) = m^2 + mn + mn + n^2 = m^2 + 2mn + n^2(m-n)(m-n) = m^2 - mn - mn + n^2 = m^2 - 2mn + n^2
3) (x-y)(x+y) = x^2 - xy + xy - y^2 = x^2 - y^2(x+y)(x+y) = x^2 + xy + xy + y^2 = x^2 + 2xy + y^2(x-y)(x-y) = x^2 - xy - xy + y^2 = x^2 - 2xy + y^2
4) (d-k)(d+k) = d^2 - dk + dk - k^2 = d^2 - k^2(d-k)(d-k) = d^2 - dk - dk + k^2 = d^2 - 2dk + k^2(d+k)(d+k) = d^2 + dk + dk + k^2 = d^2 + 2dk + k^2
1) (a-b)(a+b) = a^2 - ab + ab - b^2 = a^2 - b^2
(a-b)(a-b) = a^2 - ab - ab + b^2 = a^2 - 2ab + b^2
(a+b)(a+b) = a^2 + ab + ab + b^2 = a^2 + 2ab + b^2
2) (m-n)(m+n) = m^2 - mn + mn - n^2 = m^2 - n^2
(m+n)(m+n) = m^2 + mn + mn + n^2 = m^2 + 2mn + n^2
(m-n)(m-n) = m^2 - mn - mn + n^2 = m^2 - 2mn + n^2
3) (x-y)(x+y) = x^2 - xy + xy - y^2 = x^2 - y^2
(x+y)(x+y) = x^2 + xy + xy + y^2 = x^2 + 2xy + y^2
(x-y)(x-y) = x^2 - xy - xy + y^2 = x^2 - 2xy + y^2
4) (d-k)(d+k) = d^2 - dk + dk - k^2 = d^2 - k^2
(d-k)(d-k) = d^2 - dk - dk + k^2 = d^2 - 2dk + k^2
(d+k)(d+k) = d^2 + dk + dk + k^2 = d^2 + 2dk + k^2