Question 3(iv) Simplify: (a+b)(c-d)+(a-b)(c+d)+2(ac+bd)
(a+b)(c-d)+(a-b)(c+d)+2(ac+bd) =a(c-d)+b(c-d)+a(c+d)-b(c+d)+2ac+2bd =ac-ad+bc-bd+ac+ad-bc-bd+2ac+2bd =ac+ac-ad+ad+bc-bc-bd-bd+2ac+2bd =4ac
Question 5 ABCD is a quadrilateral. Is AB + BC + CD + DA < 2 (AC + BD)?