A) 4
B) 2
C) 1
D) - 4
Correct Answer: A
Solution :
For this to represent straight lines \[abc+2fgh-a{{f}^{2}}-b{{g}^{2}}-c{{h}^{2}}=0\] Here, a = 2, b = 3, c = k, f = ?7/2, g = ?9/2, h = 7/2. Þ \[2.3.k+2(-7/2)(-9/2)(7/2)-2{{(-7/2)}^{2}}\] \[-3{{(-9/2)}^{2}}-k{{(7/2)}^{2}}=0\] Þ \[6k+\frac{441}{4}-\frac{49}{2}-\frac{243}{4}-\frac{49k}{4}=0\] Þ \[24k+441-98-243-49k=0\] Þ \[-25k+100=0\]Þ \[k=4\].
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