If the system of equations 7x+ky=27 and kx+7y=19 have unique solution, then which one of the following is correct?

Explanation

For a unique solution, \frac{a_1}{a_2} \neq \frac{b_1}{b_2}. Therefore, \frac{7}{k} \neq \frac{k}{7} \implies k^2 \neq 49 \implies k \neq 7 and k \neq -7. Option (a) is correct.

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