question_answer

If \[x\ne 0\], \[y\ne 0\], \[z\ne 0\] and , then \[{{x}^{-1}}+{{y}^{-1}}+{{z}^{-1}}\] is equal to

A)  \[-\,1\]             

B)  \[-\,2\]

C)  \[-\,3\]             

D)  none of these

Correct Answer: C

Solution :

[c] \[=2xyz\left( 3+\frac{1}{x}+\frac{1}{y}+\frac{1}{z} \right)\] Hence, the given equation gives \[{{x}^{-1}}+{{y}^{-1}}+{{z}^{-1}}=-3.\]