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NDA 2018 Maths · Mathematics · Straight Lines · medium

The centre of the circle 3x^2+3y^2-12x+18y-5=0 is

Single correct option

The centre of the circle 3x2+3y2−12x+18y−5=03x^2+3y^2-12x+18y-5=0 is
  1. A. (−2,3)(-2,3)
  2. B. (6,−9)(6,-9)
  3. C. (2,−3)(2,-3)
  4. D. (4,−6)(4,-6)
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Answer: (C) (2,−3)(2,-3)

Divide by 3: x2+y2−4x+6y−53=0x^2+y^2-4x+6y-\frac53=0. The centre is (−−42,−62)=(2,−3)\left(-\frac{-4}{2},-\frac62\right)=(2,-3). The point (4,−6)(4,-6) forgets to halve the coefficients, and (6,−9)(6,-9) is obtained by not dividing by 3 first.
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Original question written in the NDA 2018 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake