The point of intersection of the lines $\left(a^3+3\right) x+a y+a-3=0$ and $\left(a^5+2\right) x+(a+2) y+2…

The point of intersection of the lines $\left(a^3+3\right) x+a y+a-3=0$ and $\left(a^5+2\right) x+(a+2) y+2 a+3=0$ (a real) lies on the $y$-axis for
  1. no value of $a$
  2. more than two values of $a$
  3. exactly one value of $a$
  4. exactly two values of $a$

Solution

Given equation of lines are $\left(a^3+3\right) x+a y+a-3=0$ and $\left(a^5+2\right) x+(a+2) y+2 a+3=0$ (a real) Since point of intersection of lines lies on $\mathrm{y}$-axis. $\therefore$ Put $x=0$ in each equation, we get $a \mathrm{y}+a-3=0$ and $(a+2) y+2 a+3=0$ On solving these we get $ \begin{aligned} & (a+2)(a-3)-a(2 a+3)=0 \\ & \Rightarrow a^2-a-6-2 a^2-3 a=0 \\ & \Rightarrow \quad-a^2-4 a-6=0 \Rightarrow a^2+4 a+6=0 \\ & \Rightarrow \quad a=\frac{-4 \pm \sqrt{16-24}}{2}=\frac{-4 \pm \sqrt{-8}}{2} \\ & (\text { not real) } \end{aligned} $ This shows that the point of intersection of the lines lies on the $y$-axis for no value of ' $a$ '

Asked in: JEE Main 2012 (07 May Online)

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