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Question: Answered & Verified by Expert
If the circle $x^2+y^2-6 x-8 y+\left(25-a^2\right)=0$ touches the axis of $x$, then a equals.
MathematicsCircleJEE MainJEE Main 2013 (23 Apr Online)
Options:
  • A
    0
  • B
    $\pm 4$
  • C
    $\pm 2$
  • D
    $\pm 3$
Solution:
1168 Upvotes Verified Answer
The correct answer is:
$\pm 4$


$$
\begin{aligned}
& x^2+y^2-6 x-8 y+\left(25-a^2\right)=0 \\
& \text { Radius }=4=\sqrt{9+16+\left(25-a^2\right)} \\
& \Rightarrow \mathrm{a}=\pm 4
\end{aligned}
$$

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