If a2 + b2 + c2 + 84 = 4(a - 2b + 4c), then $$\sqrt {ab - bc + ca} $$ is equal to:
A. $$4\sqrt {10} $$
B. $$\sqrt {10} $$
C. $$5\sqrt {10} $$
D. $$2\sqrt {10} $$
Answer: Option D
Solution(By Examveda Team)
$$\eqalign{ & {a^2} + {b^2} + {c^2} + 84 = 4\left( {a - 2b + 4c} \right) \cr & a = 2 \cr & b = - 4 \cr & c = 8 \cr & = \sqrt {ab - bc + ca} \cr & = \sqrt {2 \times \left( { - 4} \right) - \left( { - 4} \right) \times 8 + 8 \times 2} \cr & = \sqrt {32 + 8} \cr & = \sqrt {40} \cr & = 2\sqrt {10} \cr} $$Related Questions on Algebra
If $$p \times q = p + q + \frac{p}{q}{\text{,}}$$ then the value of 8 × 2 is?
A. 6
B. 10
C. 14
D. 16
A. $$1 + \frac{1}{{x + 4}}$$
B. x + 4
C. $$\frac{1}{x}$$
D. $$\frac{{x + 4}}{x}$$
A. $$\frac{{20}}{{27}}$$
B. $$\frac{{27}}{{20}}$$
C. $$\frac{6}{8}$$
D. $$\frac{8}{6}$$
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