Find the values of $k$ for which the line $(k-3) x-\left(4-k^{2}\right) y+k^{2}-7 k+6=0$ is
(a) Parallel to the $x$-axis,
(b) Parallel to the $y$-axis,
(c) Passing through the origin.
The given equation of line is
$(k-3) x-\left(4-k^{2}\right) y+k^{2}-7 k+6=0 \ldots(1)$
(a) If the given line is parallel to the x-axis, then
Slope of the given line = Slope of the x-axis
The given line can be written as
$\left(4-k^{2}\right) y=(k-3) x+k^{2}-7 k+6=0$
$y=\frac{(k-3)}{\left(4-k^{2}\right)} x+\frac{k^{2}-7 k+6}{\left(4-k^{2}\right)}$, which is of the form $y=m x+c$
$\therefore$ Slope of the given line $=\frac{(k-3)}{\left(4-k^{2}\right)}$
Slope of the x-axis = 0
$\therefore \frac{(k-3)}{\left(4-k^{2}\right)}=0$
$\Rightarrow k-3=0$
$\Rightarrow k=3$
Thus, if the given line is parallel to the x-axis, then the value of k is 3.
(b) If the given line is parallel to the y-axis, it is vertical. Hence, its slope will be undefined.
The slope of the given line is $\frac{(k-3)}{\left(4-k^{2}\right)}$.
Now, $\frac{(k-3)}{\left(4-k^{2}\right)}$ is undefined at $k^{2}=4$
$k^{2}=4$
$\Rightarrow k=\pm 2$
Thus, if the given line is parallel to the y-axis, then the value of k is ±2.
(c) If the given line is passing through the origin, then point (0, 0) satisfies the
given equation of line.
$(k-3)(0)-\left(4-k^{2}\right)(0)+k^{2}-7 k+6=0$
$k^{2}-7 k+6=0$
$k^{2}-6 k-k+6=0$
$(k-6)(k-1)=0$
$k=1$ or 6
Thus, if the given line is passing through the origin, then the value of k is either 1 or 6.
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