a,b,cϵR -{0} are in H.P. Then b+ab−a+b+cb−c is equal to
1
2
-2
-1
b=2aca+c⇒ba=2ca+c⇒b+ab−a=3c+ac−a Similiarly bc=2aa+c⇒b+cb−c=3a+ca−c ∴b+ab−c+b+cb−c=3a+c−(3c+a)a−c=2(a−c)a−c=2