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If a2 + b2 + 4c2 = 2(a + b - 2c) - 3 and a, b, c are real, then the value of (a2 + b2 + c2) is?
Answer & Solution
Correct Answer:
Option
D
$$\eqalign{
& {a^2} + {b^2} + 4{c^2} = 2\left( {a + b - 2c} \right) - 3 \cr
& \Rightarrow {a^2} + {b^2} + 4{c^2} - 2a - 2b + 4c + 3 = 0 \cr
& \Rightarrow {a^2} - 2a + 1 + {b^2} - 2b + 1 + 4{c^2} + 4c + 1 = 0 \cr
& \Rightarrow {\left( {a - 1} \right)^2} + {\left( {b - 1} \right)^2} + {\left( {2c + 1} \right)^2} = 0 \cr
& \cr
& \therefore a - 1 = 0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,a = 1 \cr
& \,\,\,\,\,\,\,b - 1 = 0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,b = 1 \cr
& \,\,\,\,2c + 1 = 0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,c = \frac{{ - 1}}{2} \cr
& \cr
& \therefore {a^2} + {b^2} + {c^2} \cr
& \Rightarrow 1 + 1 + \frac{1}{4} \cr
& \Rightarrow 2 + \frac{1}{4} \cr
& \Rightarrow \frac{9}{4} \cr
& \Rightarrow 2\frac{1}{4} \cr} $$
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