SSC CPO SI and ASI Model Paper 4

Question : 128 of 200

Marks: +1, -0

If a + b + c = 0, then {a ^2+ b ^2+ c^2} /{c^2 –ab} = ?

Solution:

a + b + c = 0
a+b = –c
Squaring both sides

a^2 + b^2 + 2ab = c^2 ……(i)

∴5({ a^2 + b ^2+ c^2}/{c^2 –ab})=

5 ({a^2 + b^2 + a^2 + b^2 +2ab}/ {a^2 + b^2 + 2ab –ab})

.. . by i

=5({2 (a^2 + b^2 + ab)}/{a^2 + b^2 + ab})

= 10

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