If the power of the point ( 1 , 6 ) with respect to the circle x 2 + y 2 + 4 x - 6 y - a = 0 is - 16 then a…

If the power of the point (1,6) with respect to the circle x2+y2+4x-6y-a=0 is -16 then a'' equals
  1. 5
  2. 11
  3. 21
  4. 6

Solution

As we know, power of a point x1,y1 w.r.t. the circle is x12+y12+2gx1+2fy1+C

So, Power of point 1,6=12+62+4×1-6×6-a

⇒-16=5-a

⇒a=21

Asked in: AP EAMCET 2021 (20 Aug Shift 2)

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