Q53 / 125 · BITSAT 2020 · Mathematics
If the coordinates at one end of a diameter of the circle $x^{2}+y^{2}-8 x-4 y+c=0$ are (-3,2) , then the coordinates at the other end are
- A(5,3)
- B(6,2)
- C(1,-8)
- Correct answerD(11,2)
Solution
The centre of the given circle is $\mathrm{C} \equiv(4,2)$
Let $A \equiv(-3,2)$

If $(\alpha, \beta)$ are the coordinates of the other end of the diameter, then, as the middle ploint of the diameter is the centre, $\therefore \quad \frac{\alpha-3}{2}=4$ and $\frac{\beta+2}{2}=2 \Rightarrow \alpha=11, \beta=2$ Thus, the coordinates of the other end of diameter are (11,2)

If $(\alpha, \beta)$ are the coordinates of the other end of the diameter, then, as the middle ploint of the diameter is the centre, $\therefore \quad \frac{\alpha-3}{2}=4$ and $\frac{\beta+2}{2}=2 \Rightarrow \alpha=11, \beta=2$ Thus, the coordinates of the other end of diameter are (11,2)
Hence, the correct answer is option: 'D'.