JEE MAIN - Mathematics (2024 - 27th January Evening Shift - No. 26)
If the sum of squares of all real values of $$\alpha$$, for which the lines $$2 x-y+3=0,6 x+3 y+1=0$$ and $$\alpha x+2 y-2=0$$ do not form a triangle is $$p$$, then the greatest integer less than or equal to $$p$$ is _________.
Answer
32
Explanation
$$\begin{aligned} & 2 x-y+3=0 \\ & 6 x+3 y+1=0 \\ & \alpha x+2 y-2=0 \end{aligned}$$
Will not form a $$\Delta$$ if $$\alpha x+2 y-2=0$$ is concurrent with $$2 x-y+3=0$$ and $$6 x+3 y+1=0$$ or parallel to either of them so
Case-1: Concurrent lines
$$\left|\begin{array}{ccc} 2 & -1 & 3 \\ 6 & 3 & 1 \\ \alpha & 2 & -2 \end{array}\right|=0 \Rightarrow \alpha=\frac{4}{5}$$
Case-2 : Parallel lines
$$\begin{aligned} & -\frac{\alpha}{2}=\frac{-6}{3} \text { or }-\frac{\alpha}{2}=2 \\ & \Rightarrow \alpha=4 \text { or } \alpha=-4 \\ & P=16+16+\frac{16}{25} \\ & {[P]=\left[32+\frac{16}{25}\right]=32} \end{aligned}$$
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