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