a2+b2−c2−d2+2ab−2cd.
Given:
a2+b2−c2−d2+2ab−2cd
=a2+b2+2ab−c2−d2−2cd=(a2+b2+2ab)−(c2+d2+2cd)=(a+b)2−(c+d)2=(a+b+c+d)(a+b−c−d) [∵(x2−y2=(x+y)(x−y)]
∴a2+b2−c2−d2+2ab−2cd=(a+b+c+d)(a+b−c−d)
Hence, Option A is correct.
If (a + b +c + d) (a -b- c+ d)
=(a + b- c- d) (a -b+c- d);
prove that : a : b =c : d.
Why is ab+bc+cd+da a monomial?