Factorise:
2(ab+cd)−a2−b2+c2+d2
2(ab+cd)−a2−b2+c2+d2⇒2ab+2cd−a2−b2+c2+d2⇒(c2+d2+2cd)−(a2+b2−2ab)⇒(c+d)2−(a−b)2⇒(c+d+a−b)(c+d−a+b)
If a, b, c, d are in G.p., prove that :
(i) (a2+b2),(b2+c2),(c2+d)2 are in G.P.
(ii) (a2−b2),(b2−c2),(c2−d)2 are in G.P.
(iii) 1a2+b2,1b2+c2,1c2+d2 are in G.P.
(iv) (a2+b2+c2),(ab+bc+cd),(b2+c2+d2)