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  1. If a + b + c = 0, then
    bc
    +
    ca
    +
    ab
    = ?
    bc − a2ca − b2ab − c2
    1. 1
    2. –1
    3. 0
    4. 2
Correct Option: A

a + b + c = 0
⇒ a = – b – c
⇒ a² = – ab – ac
∴ bc – a² = bc + ab + ac
Similarly,
ca – b² = ca + ab + bc
ab – c² = ab + bc + ca

bc
+
ca
+
ab
bc - a²ca - b²ab - c²

=
bc
+
ca
+
ab
ab + bc + caab + bc + caab + bc + ca

=
ba + bc + ca
= 1
ab + bc + ca



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