CAT 2020 Slot 3 QA Question & Solution
AlgebraMedium
Question
Let k be a constant. The equations $kx + y = 3$ and $4x + ky = 4$ have a unique solution if and only if
Options
$\mid k\mid
eq2$
$\mid k\mid=2$
$k
eq2$
$k=2$
Solution
Two linear equations $ax+by=c$ and $dx+ey=f$ have a unique solution if $\frac{a}{d} e \frac{b}{e}$
Therefore, $\frac{k}{4} e \frac{1}{k} \Rightarrow k^2 e 4$
$\Rightarrow k e \pm 2$