Question

Find value of k so that x=-1 and y=-1 is a solution of equation 9kx+12ky=63.

Answer 1

$9k \times ( - 1) + 12k \times ( - 1) = 63 \\ - 9k - 12k = 63 \\ - 21k = 63 \\ k = - 63 \div 21 \\ k = - 3$
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