Question

运用平方差公式计算：(a-b+c-d)(a+b-c-d)

Answer 1

=((a-d)+(b-c))*((a-d)-(b-c))

=(a-d)^2-(b-c)^2

=a^2-2ad+d^2-b^2+2bc-c^2

=a^2-b^2-c^2+d^2-2ad+2bc